# Directives

In this section we describe each of the directives that can be used in specification files. All directives begin with `%` as the first non-whitespace character in a line. The format of a generic directive is shown below.

    %Directive(arg = value, ...)
    {
        %Sub-directive
        ...
    };

A directive may have a number of arguments enclosed in parentheses followed by a number of sub-directives enclosed in braces. Individual arguments and sub-directives may be optional.

Arguments may be specified in any order. If no arguments are specified then the parentheses can be omitted. If a directive has only one compulsory argument then its value may be specified after the directive name and instead of the parentheses.

Sub-directives may be specified in any order. If no sub-directives are specified then the braces can be omitted.

If a directive is used to specify handwritten code then it may not have sub-directives. In this case the format is:

    %Directive(arg = value, ...)
        code
    %End

Ordinary C/C++ statements may also have sub-directives. These will also be enclosed in braces.

In the following descriptions arguments or blocks are shown in italics. Optional arguments are enclosed in [brackets].

Some directives are used to specify handwritten code. Handwritten code must not define names that start with the prefix `sip`.

## `%AccessCode`

    %AccessCode
        code
    %End

This sub-directive is used in the declaration of an instance of a wrapped class or structure, or a pointer to such an instance. You use it to provide handwritten code that overrides the default behaviour.

For example:

    class Klass;

    Klass *klassInstance
    {
        %AccessCode
            // In this contrived example the C++ library we are wrapping
            // defines klassInstance as Klass ** (which SIP doesn't support) so
            // we explicitly dereference it.
            if (klassInstance && *klassInstance)
                return *klassInstance;

            // This will get converted to None.
            return 0;
        %End
    };

See also

`%GetCode`, `%SetCode`

## `%AutoPyName`

    %AutoPyName(remove_leading = string)

This is a sub-directive of the `%Module` directive used to specify a rule for automatically providing Python names for classes, enums, functions, methods, variables and exceptions. The directive may be specified any number of times and each rule will be applied in turn. Rules will not be applied if an item has been given an explicit Python name.

`remove_leading` is a string that will be removed from the beginning of any C++ or C name.

For example:

    %Module PyQt5.QtCore
    {
        %AutoPyName(remove_leading="Q")
    }

## `%BIGetBufferCode`

    %BIGetBufferCode
        code
    %End

This directive (along with `%BIReleaseBufferCode`) is used to specify code that implements Python’s buffer interface.

The variables that are made available to the handwritten code depend on whether or not the limited Python API is enabled or not. The following variables are made available:

sipBufferDef *sipBuffer

  When the use of the limited API is enabled, this is a pointer to a structure that should be populated by the code. The `bd_buffer` field should be set to the address of the buffer. The `bd_length` field should be set to the length of the buffer. The `bd_readonly` field should be set to a non-zero value if the buffer is read-only.

Py_buffer *sipBuffer

  When the use of the limited Python API is disabled, this is a pointer to the Python buffer structure that should be populated by the code.

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class.

int sipFlags

  When the use of the limited Python API is disabled, these are the flags that specify what elements of the `sipBuffer` structure must be populated.

int sipRes

  The handwritten code should set this to 0 if there was no error or -1 if there was an error.

PyObject *sipSelf

  This is the Python object that wraps the structure or class instance, i.e. `self`.

## `%BIReleaseBufferCode`

    %BIReleaseBufferCode
        code
    %End

This directive (along with `%BIGetBufferCode`) is used to specify code that implements Python’s buffer interface.

The variables that are made available to the handwritten code depend on whether or not the limited Python API is enabled or not. The following variables are made available:

Py_buffer *sipBuffer

  When the use of the limited Python API is disabled, this is a pointer to the Python buffer structure.

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class.

PyObject *sipSelf

  This is the Python object that wraps the structure or class instance, i.e. `self`.

## `%CompositeModule`

    %CompositeModule(name = dotted-name)
    {
        [%Docstring]
    };

A composite module is one that merges a number of related SIP generated modules. For example, a module that merges the modules `a_mod`, `b_mod` and `c_mod` is equivalent to the following pure Python module:

    from a_mod import *
    from b_mod import *
    from c_mod import *

Clearly the individual modules should not define module-level objects with the same name.

This directive is used to specify the name of a composite module. Any subsequent `%Module` directive is interpreted as defining a component module.

The optional `%Docstring` sub-directive is used to specify the module’s docstring.

For example:

    %CompositeModule PyQt5.Qt
    %Include QtCore/QtCoremod.sip
    %Include QtGui/QtGuimod.sip

The main purpose of a composite module is as a programmer convenience as they don’t have to remember which individual module an object is defined in.

## `%ConvertFromTypeCode`

    %ConvertFromTypeCode
        code
    %End

This directive is used as part of the `%MappedType` directive or of a class specification to specify the handwritten code that converts an instance of a C/C++ type to a Python object.

If used as part of a class specification then instances of the class will be automatically converted to the Python object, even though the class itself has been wrapped. This behaviour can be changed on a temporary basis from an application by calling the `sip.enableautoconversion()` function, or from handwritten code by calling the `sipEnableAutoconversion()` function.

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the C/C++ instance to be converted. It will never be zero as the conversion from zero to `Py_None` is handled before the handwritten code is called.

PyObject *sipTransferObj

  This specifies any desired ownership changes to the returned object. If it is `NULL` then the ownership should be left unchanged. If it is `Py_None` then ownership should be transferred to Python. Otherwise ownership should be transferred to C/C++ and the returned object associated with sipTransferObj. The code can choose to interpret these changes in any way. For example, if the code is converting a C++ container of wrapped classes to a Python list it is likely that the ownership changes should be made to each element of the list.

The handwritten code must explicitly return a `PyObject *`. If there was an error then a Python exception must be raised and `NULL` returned.

The following example converts a `QList<QWidget *>` instance to a Python list of `QWidget` instances:

    %ConvertFromTypeCode
        PyObject *l;

        // Create the Python list of the correct length.
        if ((l = PyList_New(sipCpp->size())) == NULL)
            return NULL;

        // Go through each element in the C++ instance and convert it to a
        // wrapped QWidget.
        for (int i = 0; i < sipCpp->size(); ++i)
        {
            QWidget *w = sipCpp->at(i);
            PyObject *wobj;

            // Get the Python wrapper for the QWidget instance, creating a new
            // one if necessary, and handle any ownership transfer.
            if ((wobj = sipConvertFromType(w, sipType_QWidget, sipTransferObj)) == NULL)
            {
                // There was an error so garbage collect the Python list.
                Py_DECREF(l);
                return NULL;
            }

            // Add the wrapper to the list.
            PyList_SET_ITEM(l, i, wobj);
        }

        // Return the Python list.
        return l;
    %End

## `%ConvertToSubClassCode`

    %ConvertToSubClassCode
        code
    %End

This directive is fully described in Writing %ConvertToSubClassCode.

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the C++ class instance. It’s type is the base class of the convertor.

void **sipCppRet

  When the sub-class is derived from more than one super-class then it is possible that the C++ address of the instance as the sub-class is different to that of the super-class. If so, then this must be set to the C++ address of the instance when cast (usually using `static_cast`) from the super-class to the sub-class.

const sipTypeDef *sipType

  The handwritten code must set this to the SIP generated type structure that corresponds to the class instance. (The type structure for class `Klass` is `sipType_Klass`.) If the RTTI of the class instance isn’t recognised then `sipType` must be set to `NULL`. The code doesn’t have to recognise the exact class, only the most specific sub-class that it can.

  The code may also set the value to a type that is apparently unrelated to the requested type. If this happens then the whole conversion process is started again using the new type as the requested type. This is typically used to deal with classes that have more than one super-class that are subject to this conversion process. It allows the code for one super-class to switch to the code for another (more appropriate) super-class.

The handwritten code must not explicitly return.

The following example shows the sub-class conversion code for `QEvent` based class hierarchy in PyQt5:

    class QEvent
    {
    %ConvertToSubClassCode
        // QEvent sub-classes provide a unique type ID.
        switch (sipCpp->type())
        {
        case QEvent::Timer:
            sipType = sipType_QTimerEvent;
            break;

        case QEvent::KeyPress:
        case QEvent::KeyRelease:
            sipType = sipType_QKeyEvent;
            break;

        // Skip the remaining event types to keep the example short.

        default:
            // We don't recognise the type.
            sipType = NULL;
        }
    %End

        // The rest of the class specification.

    };

## `%ConvertToTypeCode`

    %ConvertToTypeCode
        code
    %End

This directive is used to specify the handwritten code that converts a Python object to a C/C++ instance and to handle any ownership transfers. It is used as part of the `%MappedType` directive and as part of a class specification. The code is also called to determine if the Python object is of the correct type prior to conversion.

When used as part of a class specification it can automatically convert additional types of Python object.

The following variables are made available to the handwritten code:

int *sipIsErr

  If this is `NULL` then the code is being asked to check the type of the Python object. The check must not have any side effects. Otherwise the code is being asked to convert the Python object and a non-zero value should be returned through this pointer if an error occurred during the conversion.

PyObject *sipPy

  This is the Python object to be converted.

type **sipCppPtr

  This is a pointer through which the address of the mapped type instance (or zero if appropriate) is returned. Its value is undefined if `sipIsErr` is `NULL`.

PyObject *sipTransferObj

  This specifies any desired ownership changes to sipPy. If it is `NULL` then the ownership should be left unchanged. If it is `Py_None` then ownership should be transferred to Python. Otherwise ownership should be transferred to C/C++ and sipPy associated with sipTransferObj. The code can choose to interpret these changes in any way.

void **sipUserStatePtr

  This is a pointer through which a mapped type convertor can store additional state information. Any value set will be passed to the code defined by the corresponding `%ReleaseCode` directive invoked by a call to `sipReleaseTypeUS()`.

The handwritten code must explicitly return an `int` the meaning of which depends on the value of `sipIsErr`.

If `sipIsErr` is `NULL` then a non-zero value is returned if the Python object has a type that can be converted to the mapped type. Otherwise zero is returned.

If `sipIsErr` is not `NULL` then a combination of the following flags is returned.

> - `SIP_TEMPORARY` is set to indicate that the returned instance is a temporary and should be released, by calling `sipReleaseType()` or `sipReleaseTypeUS()`, to avoid a memory leak.

> - `SIP_DERIVED_CLASS` is set by a class convertor to indicate that the type of the returned instance is a derived class. See Generated Derived Classes.

> - `SIP_USER` is a flag that can be returned by a mapped type convertor. It will be passed to the code defined by a corresponding `%ReleaseCode` directive.

The following example converts a Python list of `QPoint` instances to a `QList<QPoint>` instance:

    %ConvertToTypeCode
        // See if we are just being asked to check the type of the Python
        // object.
        if (!sipIsErr)
        {
            // Checking whether or not None has been passed instead of a list
            // has already been done.  Note that we don't check the type of the
            // individual elements of the list.
            return PyList_Check(sipPy);
        }

        // Create the instance on the heap.
        QList<QPoint> *ql = new QList<QPoint>;

        for (int i = 0; i < PyList_GET_SIZE(sipPy); ++i)
        {
            QPoint *qp;
            int state;

            // Get the address of the element's C++ instance.  Note that, in
            // this case, we don't apply any ownership changes to the list
            // elements, only to the list itself.
            qp = reinterpret_cast<QPoint *>(
                    sipForceConvertToType(PyList_GET_ITEM(sipPy, i),
                            sipType_QPoint, 0, SIP_NOT_NONE, &state,
                            sipIsErr));

            // Deal with any errors.
            if (*sipIsErr)
            {
                sipReleaseType(qp, sipType_QPoint, state);

                // Tidy up.
                delete ql;

                // There is no temporary instance.
                return 0;
            }

            ql->append(*qp);

            // A copy of the QPoint was appended to the list so we no longer
            // need it.  It may be a temporary instance that should be
            // destroyed, or a wrapped instance that should not be destroyed.
            // sipReleaseType() will do the right thing.
            sipReleaseType(qp, sipType_QPoint, state);
        }

        // Return the instance.
        *sipCppPtr = ql;

        // The instance should be regarded as temporary (and be destroyed as
        // soon as it has been used) unless it has been transferred from
        // Python.  sipGetState() is a convenience function that implements
        // this common transfer behaviour.
        return sipGetState(sipTransferObj);
    %End

When used in a class specification the handwritten code replaces the code that would normally be automatically generated. This means that the handwritten code must also handle instances of the class itself and not just the additional types that are being supported. This should be done by making calls to `sipCanConvertToType()` to check the object type and `sipConvertToTypeUS()` or `sipConvertToType()` to convert the object. The `SIP_NO_CONVERTORS` flag must be passed to these functions to prevent recursive calls to the handwritten code.

## `%Copying`

    %Copying
        text
    %End

This directive is used to specify some arbitrary text that will be included at the start of all source files generated by SIP. It is normally used to include copyright and licensing terms.

For example:

    %Copying
    Copyright (c) 2019 Riverbank Computing Limited
    %End

## `%DefaultDocstringFormat`

    %DefaultDocstringFormat(name = ["raw" | "deindented"])

This directive is used to specify the default formatting of docstrings, i.e. when the `%Docstring` directive does not specify an explicit format.

See the `%Docstring` directive for an explanation of the different formats. If the directive is not specified then the default format used is `"raw"`.

For example:

    %DefaultDocstringFormat "deindented"

## `%DefaultDocstringSignature`

    %DefaultDocstringSignature(name = ["discarded" | "prepended" | "appended"])

This directive is used to specify the default positioning of signatures in docstrings, i.e. when the `%Docstring` directive is used but does not specify an explicit positioning.

See the `%Docstring` directive for an explanation of the different ways signatures are positioned. If the directive is not specified then the default positioning is `"discarded"`.

For example:

    %DefaultDocstringSignature "prepended"

## `%DefaultEncoding`

    %DefaultEncoding(name = ["ASCII" | "Latin-1" | "UTF-8" | "None"])

This directive is used to specify the default encoding used for `char`, `const char`, `char *` or `const char *` values. An encoding of `"None"` means that the value is unencoded. The default can be overridden for a particular value using the `Encoding` annotation.

If the directive is not specified then the default encoding of the last imported module is used, if any.

For example:

    %DefaultEncoding "Latin-1"

## `%DefaultMetatype`

    %DefaultMetatype(name = dotted-name)

This directive is used to specify the Python type that should be used as the meta-type for any C/C++ data type defined in the same module, and by importing modules, that doesn’t have an explicit meta-type.

If this is not specified then `sip.wrappertype` is used.

You can also use the `Metatype` class annotation to specify the meta-type used by a particular C/C++ type.

See the section Types and Meta-types for more details.

For example:

    %DefaultMetatype PyQt5.QtCore.pyqtWrapperType

## `%DefaultSupertype`

    %DefaultSupertype(name = dotted-name)

This directive is used to specify the Python type that should be used as the super-type for any C/C++ data type defined in the same module that doesn’t have an explicit super-type.

If this is not specified then `sip.wrapper` is used.

You can also use the `Supertype` class annotation to specify the super-type used by a particular C/C++ type.

See the section Types and Meta-types for more details.

For example:

    %DefaultSupertype sip.simplewrapper

## `%Docstring`

    %Docstring(format = ["raw" | "deindented"], signature = ["discarded" | "prepended" | "appended"])
        text
    %End

This directive is used to specify explicit docstrings for modules, classes, functions, methods, typedefs and properties.

The docstring of a class is made up of the docstring specified for the class itself, with the docstrings specified for each contructor appended.

The docstring of a function or method is made up of the concatenated docstrings specified for each of the overloads.

Note

Specifying an explicit docstring will mean that SIP will generate less informative exceptions (i.e. without a full signature) when it fails to match a set of arguments to any function or method overload.

`format` may either be `"raw"` or `"deindented"`. If it is not specified then the value specified by any `%DefaultDocstringFormat` directive is used.

If `format` is `"raw"` then the docstring is used as it appears in the specification file.

If `format` is `"deindented"` then any leading spaces common to all non-blank lines of the docstring are removed.

`signature` may either be `"discarded"`, `"prepended"` or `"appended"`. It is ignored unless applied to the docstring of a class, function or method. If it is not specified then the value specified by any `%DefaultDocstringSignature` directive is used.

If `signature` is `"discarded"` then the automatically generated function or method signature is discarded. In the context of a class’s docstring then this refers to all of the constructors’ docstrings.

If `signature` is `"prepended"` then the automatically generated function or method signature is placed before the docstring. In the context of a class’s docstring then this refers to all of the constructors’ docstrings.

If `signature` is `"appended"` then the automatically generated function or method signature is placed after the docstring. In the context of a class’s docstring then this refers to all of the constructors’ docstrings.

For example:

    class Klass
    {
    %Docstring
    This will be at the start of the class's docstring.
    %End

    public:
        Klass();
    %Docstring "deindented"
        This will be appended to the class's docstring and will not be indented.

            This will be indented by four spaces.
    %End
    };

See also

`%DefaultDocstringFormat`, `%DefaultDocstringSignature`

## `%End`

This isn’t a directive in itself, but is used to terminate a number of directives that allow a block of handwritten code or text to be specified.

## `%Exception`

    %Exception name [(base-exception)]
    {
        [%TypeHeaderCode]
        %RaiseCode
    };

This directive is used to define new Python exceptions, or to provide a stub for existing Python exceptions. It allows handwritten code to be provided that implements the translation between C++ exceptions and Python exceptions.

The arguments to a function’s `throw ()` specifiers must either be names of classes or the names of Python exceptions defined by this directive. If a `throw ()` specifier has no arguments, or the `noexcept` specifier is used, then it is assumed that the function never raises an exception.

Note

`throw ()` specifiers are ignored (and should be omitted) when using ABI v13.1 or later and v12.9 or later.

name is the name of the exception.

base-exception is the optional base exception. This may be either one of the standard Python exceptions or one defined with a previous `%Exception` directive. If it is omitted then a new Python exception is not created.

The optional `%TypeHeaderCode` sub-directive is used to specify any external interface to the exception being defined.

The `%RaiseCode` sub-directive is used to specify the handwritten code that converts a reference to the C++ exception to the Python exception.

For example:

    %Exception std::exception(SIP_Exception) /PyName=StdException/
    {
    %TypeHeaderCode
    #include <exception>
    %End
    %RaiseCode
        const char *detail = sipExceptionRef.what();

        SIP_BLOCK_THREADS
        PyErr_SetString(sipException_std_exception, detail);
        SIP_UNBLOCK_THREADS
    %End
    };

In this example we map the standard C++ exception to a new Python exception. The new exception is called `StdException` and is derived from the standard Python exception `Exception`.

An exception may be annotated with `Default` to specify that it should be caught by default if there is no `throw` clause.

In this second example we do not create a new Python exception but instead convert the standard C++ `std::out_of_range` exception to the standard Python `IndexError` exception:

    %Exception std::out_of_range
    {
    %TypeHeaderCode
    #include <stdexcept>
    %End
    %RaiseCode
        const char *detail = sipExceptionRef.what();

        SIP_BLOCK_THREADS
        PyErr_SetString(PyExc_IndexError, detail);
        SIP_UNBLOCK_THREADS
    %End
    };

## `%ExportedHeaderCode`

    %ExportedHeaderCode
        code
    %End

This directive is used to specify handwritten code, typically the declarations of types, that is placed in a header file that is included by all generated code for all modules. It should not include function declarations because Python modules should not explicitly call functions in another Python module.

See also

`%ModuleCode`, `%ModuleHeaderCode`

## `%ExportedTypeHintCode`

    %ExportedTypeHintCode
        code
    %End

This directive is used to specify handwritten code, typically the declarations of types, that is placed in the PEP 484 type hint stub file for any module that imports it. Note that it is not included in the stub file for the module itself.

See also

`%TypeHintCode`

## `%Extract`

    %Extract(id = name [, order = integer])
        text
    %End

This directive is used to specify part of an extract. An extract is a collection of arbitrary text specified as one or more parts each having the same `id`. SIP places no interpretation on an identifier, or on the contents of the extract. Extracts may be used for any purpose, e.g. documentation, tests etc.

The part’s optional `order` determines its position relative to the extract’s other parts. If the order is not specified then the part is appended to the extract.

For example:

    %Extract example
    This will be the last line because there is no explicit order.
    %End

    %Extract(id=example, order=20)
    This will be the second line.
    %End

    %Extract(id=example, order=10)
    This will be the first line.
    %End

## `%Feature`

    %Feature(name = name)

This directive is used to declare a feature. Features (along with `%Platforms` and `%Timeline`) are used by the `%If` directive to control whether or not parts of a specification are processed or ignored.

Features are mutually independent of each other - any combination of features may be enabled or disabled. By default all features are enabled. The `disabled-features` value of the bindings section in `pyproject.toml` is used to specify any disabled features.

If a feature is enabled then SIP will automatically generate a corresponding C preprocessor symbol for use by handwritten code. The symbol is the name of the feature prefixed by `SIP_FEATURE_`.

For example:

    %Feature FOO_SUPPORT

    %If (FOO_SUPPORT)
    void foo();
    %End

## `%FinalisationCode`

    %FinalisationCode
        code
    %End

This directive is used to specify handwritten code that is executed once the instance of a wrapped class has been created. The handwritten code is passed a dictionary of any remaining keyword arguments. It must explicitly return an integer result which should be `0` if there was no error. If an error occurred then `-1` should be returned and a Python exception raised.

The following variables are made available to the handwritten code:

PyObject *sipSelf

  This is the Python object that wraps the structure or class instance, i.e. `self`.

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class.

PyObject *sipKwds

  This is an optional dictionary of unused keyword arguments. It may be `NULL` or refer to an empty dictionary. If the handwritten code handles any of the arguments then, if `sipUnused` is `NULL`, those arguments must be removed from the dictionary. If `sipUnused` is not `NULL` then the `sipKwds` dictionary must not be updated. Instead a new dictionary must be created that contains any remaining unused keyword arguments and the address of the new dictionary returned via `sipUnused`. This rather complicated API ensures that new dictionaries are created only when necessary.

PyObject **sipUnused

  This is an optional pointer to where the handwritten code should save the address of any new dictionary of unused keyword arguments that it creates. If it is `NULL` then the handwritten code is allowed to update the `sipKwds` dictionary.

## `%GCClearCode`

    %GCClearCode
        code
    %End

Python has a cyclic garbage collector which can identify and release unneeded objects even when their reference counts are not zero. If a wrapped C structure or C++ class keeps its own reference to a Python object then, if the garbage collector is to do its job, it needs to provide some handwritten code to traverse and potentially clear those embedded references.

See the section Supporting Cyclic Garbage Collection in the Python documentation for the details.

This directive is used to specify the code that clears any embedded references. (See `%GCTraverseCode` for specifying the code that traverses any embedded references.)

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class.

int sipRes

  The handwritten code should set this to the result to be returned.

The following simplified example is taken from PyQt5. The `QCustomEvent` class allows arbitary data to be attached to the event. In PyQt5 this data is always a Python object and so should be handled by the garbage collector:

    %GCClearCode
        PyObject *obj;

        // Get the object.
        obj = reinterpret_cast<PyObject *>(sipCpp->data());

        // Clear the pointer.
        sipCpp->setData(0);

        // Clear the reference.
        Py_XDECREF(obj);

        // Report no error.
        sipRes = 0;
    %End

## `%GCTraverseCode`

    %GCTraverseCode
        code
    %End

This directive is used to specify the code that traverses any embedded references for Python’s cyclic garbage collector. (See `%GCClearCode` for a full explanation.)

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class.

visitproc sipVisit

  This is the visit function provided by the garbage collector.

void *sipArg

  This is the argument to the visit function provided by the garbage collector.

int sipRes

  The handwritten code should set this to the result to be returned.

The following simplified example is taken from PyQt5’s `QCustomEvent` class:

    %GCTraverseCode
        PyObject *obj;

        // Get the object.
        obj = reinterpret_cast<PyObject *>(sipCpp->data());

        // Call the visit function if there was an object.
        if (obj)
            sipRes = sipVisit(obj, sipArg);
        else
            sipRes = 0;
    %End

## `%GetCode`

    %GetCode
        code
    %End

This sub-directive is used in the declaration of a C++ class variable or C structure member to specify handwritten code to convert it to a Python object. It is usually used to handle types that SIP cannot deal with automatically.

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class. It is not made available if the variable being wrapped is a static class variable.

PyObject *sipPy

  The handwritten code must set this to the Python representation of the class variable or structure member. If there is an error then the code must raise an exception and set this to `NULL`.

PyObject *sipPyType

  If the variable being wrapped is a static class variable then this is the Python type object of the class from which the variable was referenced (not the class in which it is defined). It may be safely cast to a PyTypeObject * or a sipWrapperType *.

For example:

    struct Entity
    {
        /*
         * In this contrived example the C library we are wrapping actually
         * defines this as char buffer[100] which SIP cannot handle
         * automatically.
         */
        char *buffer
        {
            %GetCode
                sipPy = PyString_FromStringAndSize(sipCpp->buffer, 100);
            %End

            %SetCode
                char *ptr;
                int length;

                if (PyString_AsStringAndSize(sipPy, &ptr, &length) == -1)
                {
                    sipErr = 1;
                }
                else if (length != 100)
                {
                    /*
                     * Raise an exception because the length isn't exactly
                     * right.
                     */

                    PyErr_SetString(PyExc_ValueError,
                            "an Entity.buffer must be exactly 100 bytes");
                    sipErr = 1;
                }
                else
                {
                    memcpy(sipCpp->buffer, ptr, 100);
                }
            %End
        };
    }

See also

`%AccessCode`, `%SetCode`

## `%HideNamespace`

    %HideNamespace(name = name)

This directive is used to specify that a C++ namespace, which would normally be wrapped as a Python class, is not wrapped. The contents of the namespace are still wrapped but are placed in the module dictionary. This is usually used when a library being wrapped uses a single namespace that includes everything in the library. In Python the module itself performs the same function as the namespace and so the namespace would just add an unneccessary extra level of indirection.

## `%If`

    %If (expression)
        specification
    %End

where

    expression ::= [ored-qualifiers | range]

    ored-qualifiers ::= [qualifier | qualifier || ored-qualifiers]

    qualifier ::= [!] [feature | platform]

    range ::= [version] - [version]

This directive is used in conjunction with features (see `%Feature`), platforms (see `%Platforms`) and versions (see `%Timeline`) to control whether or not parts of a specification are processed or not.

A range of versions means all versions starting with the lower bound up to but excluding the upper bound. If the lower bound is omitted then it is interpreted as being before the earliest version. If the upper bound is omitted then it is interpreted as being after the latest version.

For example:

    %Feature SUPPORT_FOO
    %Platforms {WIN32_PLATFORM POSIX_PLATFORM MACOS_PLATFORM}
    %Timeline {V1_0 V1_1 V2_0 V3_0}

    %If (!SUPPORT_FOO)
        // Process this if the SUPPORT_FOO feature is disabled.
    %End

    %If (POSIX_PLATFORM || MACOS_PLATFORM)
        // Process this if either the POSIX_PLATFORM or MACOS_PLATFORM
        // platforms are enabled.
    %End

    %If (V1_0 - V2_0)
        // Process this if either V1_0 or V1_1 is enabled.
    %End

    %If (V2_0 - )
        // Process this if either V2_0 or V3_0 is enabled.
    %End

    %If (SIP_5_1_0 - )
        // SIP v5.1.0 and later will process this.
    %End

    %If ( - )
        // Always process this.
    %End

Also note that the only way to specify the logical and of qualifiers is to use nested `%If` directives.

## `%Import`

    %Import(name = filename)

This directive is used to import the specification of another module. This is needed if the current module makes use of any types defined in the imported module, e.g. as an argument to a function, or to sub-class.

If `name` cannot be opened then SIP prepends `name` with the name of the directory containing the current specification file (i.e. the one containing the `%Import` directive) and tries again. If this also fails then SIP prepends `name` with each of the directories, in turn, specified by the `sip-include-dirs` value of the project section in `pyproject.toml`.

Directory separators must always be `/`.

For example:

    %Import QtCore/QtCoremod.sip

## `%Include`

    %Include(name = filename [, optional = [True | False]])

This directive is used to include contents of another file as part of the specification of the current module. It is the equivalent of the C preprocessor’s `#include` directive and is used to structure a large module specification into manageable pieces.

`%Include` follows the same search process as the `%Import` directive when trying to open `name`.

if `optional` is set then SIP will silently continue processing if the file could not be opened.

Directory separators must always be `/`.

For example:

    %Include qwidget.sip

## `%InitialisationCode`

    %InitialisationCode
        code
    %End

This directive is used to specify handwritten code that is embedded in-line in the generated module initialisation code after the SIP module has been imported but before the module itself has been initialised.

It is typically used to call `sipRegisterPyType()`.

For example:

    %InitialisationCode
        // The code will be executed when the module is first imported, after
        // the SIP module has been imported, but before other module-specific
        // initialisation has been completed.
    %End

## `%InstanceCode`

    %InstanceCode
        code
    %End

There are a number of circumstances where SIP needs to create an instance of a C++ class but may not be able to do so. For example the C++ class may be abstract or may not have an argumentless public constructor. This directive is used in the definition of a class or mapped type to specify handwritten code to create an instance of the C++ class. For example, if the C++ class is abstract, then the handwritten code may return an instance of a concrete sub-class.

The following variable is made available to the handwritten code:

type *sipCpp

  This must be set by the handwritten code to the address of an instance of the C++ class. It doesn’t matter if the instance is on the heap or not as it will never be explicitly destroyed.

## `%License`

    %License(type = string
            [, licensee = string]
            [, signature = string]
            [, timestamp = string])

This directive is used to specify the contents of an optional license dictionary. The license dictionary is called `__license__` and is stored in the module dictionary.

`type` is the type of the license and its value in the license dictionary is accessed using the `"Type"` key. No restrictions are placed on the value.

`licensee` is the optional name of the licensee and its value in the license dictionary is accessed using the `"Licensee"` key. No restrictions are placed on the value.

`signature` is the license’s optional signature and its value in the license dictionary is accessed using the `"Signature"` key. No restrictions are placed on the value.

`timestamp` is the license’s optional timestamp and its value in the license dictionary is accessed using the `"Timestamp"` key. No restrictions are placed on the value.

Note that this directive isn’t an attempt to impose any licensing restrictions on a module. It is simply a method for easily embedding licensing information in a module so that it is accessible to Python scripts.

For example:

    %License "GPL"

## `%MappedType`

    template<type-list>
    %MappedType type
    {
        [%TypeCode]
        [%TypeHeaderCode]
        [%ConvertToTypeCode]
        [%ConvertFromTypeCode]
        [%ReleaseCode]
    };

    %MappedType type
    {
        [%TypeCode]
        [%TypeHeaderCode]
        [%ConvertToTypeCode]
        [%ConvertFromTypeCode]
        [%ReleaseCode]
    };

This directive is used to define an automatic mapping between a C or C++ type and a Python type. It can be used as part of a template, or to map a specific type.

When used as part of a template type cannot itself refer to a template. Any occurrences of any of the type names (but not any `*` or `&`) in type-list will be replaced by the actual type names used when the template is instantiated. Template mapped types are instantiated automatically as required (unlike template classes which are only instantiated using `typedef`).

Any explicit mapped type will be used in preference to any template that maps the same type, ie. a template will not be automatically instantiated if there is an explicit mapped type.

The optional `%TypeCode` sub-directive is used to specify additional code, typically utility functions, that can be called from other handwritten code.

The optional `%TypeHeaderCode` sub-directive is used to specify the library interface to the type being mapped.

The optional `%ConvertToTypeCode` sub-directive is used to specify the handwritten code that converts a Python object to an instance of the mapped type.

The optional `%ConvertFromTypeCode` sub-directive is used to specify the handwritten code that converts an instance of the mapped type to a Python object.

The optional `%ReleaseCode` sub-directive is used to specify the handwritten code that releases an instance of the mapped type to the heap.

For example:

    template<Type *>
    %MappedType QList
    {
    %TypeHeaderCode
    // Include the library interface to the type being mapped.
    #include <qlist.h>
    %End

    %ConvertToTypeCode
        // See if we are just being asked to check the type of the Python
        // object.
        if (sipIsErr == NULL)
        {
            // Check it is a list.
            if (!PyList_Check(sipPy))
                return 0;

            // Now check each element of the list is of the type we expect.
            // The template is for a pointer type so we don't disallow None.
            for (int i = 0; i < PyList_GET_SIZE(sipPy); ++i)
                if (!sipCanConvertToType(PyList_GET_ITEM(sipPy, i),
                                         sipType_Type, 0))
                    return 0;

            return 1;
        }

        // Create the instance on the heap.
        QList<Type *> *ql = new QList<Type *>;

        for (int i = 0; i < PyList_GET_SIZE(sipPy); ++i)
        {
            // Use the SIP API to convert the Python object to the
            // corresponding C++ instance.  Note that we apply any ownership
            // transfer to the list itself, not the individual elements.
            Type *t = reinterpret_cast<Type *>(sipConvertToType(
                                                PyList_GET_ITEM(sipPy, i),
                                                sipType_Type, 0, 0, 0,
                                                sipIsErr));

            if (*sipIsErr)
            {
                // Tidy up.
                delete ql;

                // There is nothing on the heap.
                return 0;
            }

            // Add the pointer to the C++ instance.
            ql->append(t);
        }

        // Return the instance on the heap.
        *sipCppPtr = ql;

        // Apply the normal transfer.
        return sipGetState(sipTransferObj);
    %End

    %ConvertFromTypeCode
        PyObject *l;

        // Create the Python list of the correct length.
        if ((l = PyList_New(sipCpp->size())) == NULL)
            return NULL;

        // Go through each element in the C++ instance and convert it to the
        // corresponding Python object.
        for (int i = 0; i < sipCpp->size(); ++i)
        {
            Type *t = sipCpp->at(i);
            PyObject *tobj;

            if ((tobj = sipConvertFromType(t, sipType_Type, sipTransferObj)) == NULL)
            {
                // There was an error so garbage collect the Python list.
                Py_DECREF(l);
                return NULL;
            }

            PyList_SET_ITEM(l, i, tobj);
        }

        // Return the Python list.
        return l;
    %End
    };

Using this we can use, for example, `QList<QObject *>` throughout the module’s specification files (and in any module that imports this one). The generated code will automatically map this to and from a Python list of QObject instances when appropriate.

## `%MethodCode`

    %MethodCode
        code
    %End

This directive is used as part of the specification of a global function, class method, operator, constructor or destructor to specify handwritten code that replaces the normally generated call to the function being wrapped. It is usually used to handle argument types and results that SIP cannot deal with automatically.

Normally the specified code is embedded in-line after the function’s arguments have been successfully converted from Python objects to their C or C++ equivalents. In this case the specified code must not include any `return` statements.

However if the `NoArgParser` annotation has been used then the specified code is also responsible for parsing the arguments. No other code is generated by SIP and the specified code must include a `return` statement.

In the context of a destructor the specified code is embedded in-line in the Python type’s deallocation function. Unlike other contexts it supplements rather than replaces the normally generated code, so it must not include code to return the C structure or C++ class instance to the heap. The code is only called if ownership of the structure or class is with Python.

The specified code must also handle the Python Global Interpreter Lock (GIL). If compatibility with SIP v3.x is required then the GIL must be released immediately before the C++ call and reacquired immediately afterwards as shown in this example fragment:

    Py_BEGIN_ALLOW_THREADS
    sipCpp->foo();
    Py_END_ALLOW_THREADS

If compatibility with SIP v3.x is not required then this is optional but should be done if the C++ function might block the current thread or take a significant amount of time to execute. (See The Python Global Interpreter Lock and the `ReleaseGIL` and `HoldGIL` annotations.)

If the `NoArgParser` annotation has not been used then the following variables are made available to the handwritten code:

type a0

  There is a variable for each argument of the Python signature (excluding any `self` argument) named `a0`, `a1`, etc. If `use_argument_names` has been set in the `%Module` directive then the name of the argument is the real name. The type of the variable is the same as the type defined in the specification with the following exceptions:

  - if the argument is only used to return a value (e.g. it is an `int *` without an `In` annotation) then the type has one less level of indirection (e.g. it will be an `int`)

  - if the argument is a structure or class (or a reference or a pointer to a structure or class) then type will always be a pointer to the structure or class.

  Note that handwritten code for destructors never has any arguments.

PyObject *a0Wrapper

  This variable is made available only if the `GetWrapper` annotation is specified for the corresponding argument. The variable is a pointer to the Python object that wraps the argument.

  If `use_argument_names` has been set in the `%Module` directive then the name of the variable is the real name of the argument with `Wrapper` appended.

type *sipCpp

  If the directive is used in the context of a class constructor then this must be set by the handwritten code to the constructed instance. If it is set to `0` and no Python exception is raised then SIP will continue to try other Python signatures.

  If the directive is used in the context of a method (but not the standard binary operator methods, e.g. `__add__()`) or a destructor then this is a pointer to the C structure or C++ class instance.

  Its type is a pointer to the structure or class.

  Standard binary operator methods follow the same convention as global functions and instead define two arguments called `a0` and `a1`.

sipErrorState sipError

  The handwritten code should set this to either `sipErrorContinue` or `sipErrorFail`, and raise an appropriate Python exception, if an error is detected. Its initial value will be `sipErrorNone`.

  When `sipErrorContinue` is used, SIP will remember the exception as the reason why the particular overloaded callable could not be invoked. It will then continue to try the next overloaded callable. It is typically used by code that needs to do additional type checking of the callable’s arguments.

  When `sipErrorFail` is used, SIP will report the exception immediately and will not attempt to invoke other overloaded callables.

  `sipError` is not provided for destructors.

int sipIsErr

  The handwritten code should set this to a non-zero value, and raise an appropriate Python exception, if an error is detected. This is the equivalent of setting `sipError` to `sipErrorFail`. Its initial value will be `0`.

  `sipIsErr` is not provided for destructors.

type sipRes

  The handwritten code should set this to the result to be returned. The type of the variable is the same as the type defined in the Python signature in the specification with the following exception:

  - if the argument is a structure or class (or a reference or a pointer to a structure or class) then type will always be a pointer to the structure or class.

  `sipRes` is not provided for inplace operators (e.g. `+=` or `__imul__()`) as their results are handled automatically, nor for class constructors or destructors.

PyObject *sipSelf

  If the directive is used in the context of a class constructor, destructor or non-static method then this is the Python object that wraps the structure or class instance, i.e. `self`. Starting with ABI v13.0, in the context of a static method, this will contain the Python type object of the class.

bool sipSelfWasArg

  This is only made available for non-abstract, virtual methods. It is set if `self` was explicitly passed as the first argument of the method rather than being bound to the method. In other words, the call was:

      Klass.foo(self, ...)

  rather than:

      self.foo(...)

If the `NoArgParser` annotation has been used then only the following variables are made available to the handwritten code:

PyObject *sipArgs

  This is the tuple of arguments.

PyObject *sipKwds

  This is the dictionary of keyword arguments.

The following is a complete example:

    class Klass
    {
    public:
        virtual int foo(SIP_PYTUPLE);
    %MethodCode
            // The C++ API takes a 2 element array of integers but passing a
            // two element tuple is more Pythonic.

            int iarr[2];

            if (PyArg_ParseTuple(a0, "ii", &iarr[0], &iarr[1]))
            {
                Py_BEGIN_ALLOW_THREADS
                sipRes = sipSelfWasArg ? sipCpp->Klass::foo(iarr)
                                       : sipCpp->foo(iarr);
                Py_END_ALLOW_THREADS
            }
            else
            {
                // PyArg_ParseTuple() will have raised the exception.
                sipIsErr = 1;
            }
    %End
    };

As the example is a virtual method [1], note the use of `sipSelfWasArg` to determine exactly which implementation of `foo()` to call.

If a method is in the `protected` section of a C++ class then SIP generates helpers that provide access to method. However, these are not available if the Python module is being built with `protected` redefined as `public`.

The following pattern should be used to cover all possibilities:

    #if defined(SIP_PROTECTED_IS_PUBLIC)
        sipRes = sipSelfWasArg ? sipCpp->Klass::foo(iarr)
                               : sipCpp->foo(iarr);
    #else
        sipRes = sipCpp->sipProtectVirt_foo(sipSelfWasArg, iarr);
    #endif

If a method is in the `protected` section of a C++ class but is not virtual then the pattern should instead be:

    #if defined(SIP_PROTECTED_IS_PUBLIC)
        sipRes = sipCpp->foo(iarr);
    #else
        sipRes = sipCpp->sipProtect_foo(iarr);
    #endif

[1]

See `%VirtualCatcherCode` for a description of how SIP generated code handles the reimplementation of C++ virtual methods in Python.

## `%Module`

    %Module(name = dotted-name
            [, all_raise_py_exception = [True | False]]
            [, call_super_init = [True | False]]
            [, default_VirtualErrorHandler = name]
            [, keyword_arguments = ["None" | "All" | "Optional"]]
            [, language = string]
            [, py_ssize_t_clean = [True | False]]
            [, use_argument_names = [True | False]]
            [, use_limited_api = [True | False]])
    {
        [%AutoPyName]
        [%Docstring]
    };

This directive is used to specify the name of a module and a number of other attributes. `name` may contain periods to specify that the module is part of a Python package.

`all_raise_py_exception` specifies that all constructors, functions and methods defined in the module raise a Python exception to indicate that an error occurred. It is the equivalent of using the `RaisesPyException` function annotation on every constructor, function and method.

`call_super_init` specifies that the `__init__()` method of a wrapped class should automatically call it’s super-class’s `__init__()` method passing a dictionary of any unused keyword arguments. In other words, wrapped classes support cooperative multi-inheritance. This means that sub-classes, and any mixin classes, should always use call `super().__init__()` and not call any super-class’s `__init__()` method explicitly.

`default_VirtualErrorHandler` specifies the handler (defined by the `%VirtualErrorHandler` directive) that is called when a Python re-implementation of any virtual C++ function raises a Python exception. If no handler is specified for a virtual C++ function then `PyErr_Print()` is called.

`keyword_arguments` specifies the default level of support for Python keyword arguments. See the `KeywordArgs` annotation for an explaination of the possible values and their effect.

`language` specifies the implementation language of the library being wrapped. Its value is either `"C++"` (the default) or `"C"`.

`py_ssize_t_clean` specifies that the generated code should include `#define PY_SSIZE_T_CLEAN` before any `#include <Python.h>`.

When providing handwritten code as part of either the `%MethodCode` or `%VirtualCatcherCode` directives the names of the arguments of the function or method are based on the number of the argument, i.e. the first argument is named `a0`, the second `a1` and so on. `use_argument_names` is set to specify that the real name of the argument, if any, should be used instead. It also affects the name of the variable created when the `GetWrapper` argument annotation is used.

`use_limited_api` specifies that the generated code will only use the limited Python API defined in PEP 384. It also ensures that the C preprocessor symbol `Py_LIMITED_API` is defined before the `Python.h` header file is included. Python extensions built in this way are independent of the version of Python being used.

The optional `%AutoPyName` sub-directive is used to specify a rule for automatically providing Python names.

The optional `%Docstring` sub-directive is used to specify the module’s docstring.

For example:

    %Module PyQt5.QtCore

## `%ModuleCode`

    %ModuleCode
        code
    %End

This directive is used to specify handwritten code, typically the implementations of utility functions, that can be called by other handwritten code in the module.

For example:

    %ModuleCode
    // Print an object on stderr for debugging purposes.
    void dump_object(PyObject *o)
    {
        PyObject_Print(o, stderr, 0);
        fprintf(stderr, "\n");
    }
    %End

See also

`%ExportedHeaderCode`, `%ModuleHeaderCode`

## `%ModuleHeaderCode`

    %ModuleHeaderCode
        code
    %End

This directive is used to specify handwritten code, typically the declarations of utility functions, that is placed in a header file that is included by all generated code for the same module.

For example:

    %ModuleHeaderCode
    void dump_object(PyObject *o);
    %End

See also

`%ExportedHeaderCode`, `%ModuleCode`

## `%PickleCode`

    %PickleCode
        code
    %End

This directive is used to specify handwritten code to pickle a C structure or C++ class instance.

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class.

PyObject *sipRes

  The handwritten code must set this to a tuple of the arguments that will be passed to the type’s `__init__()` method when the structure or class instance is unpickled. If there is an error then the code must raise an exception and set this to `NULL`.

For example:

    class Point
    {
        Point(int x, y);

        int x() const;
        int y() const;

    %PickleCode
        sipRes = Py_BuildValue("ii", sipCpp->x(), sipCpp->y());
    %End
    }

Note that SIP works around the Python limitation that prevents nested types being pickled.

Both named and unnamed enums can be pickled automatically without providing any handwritten code.

## `%Platforms`

    %Platforms {name name ...}

This directive is used to declare a set of platforms. Platforms (along with `%Feature` and `%Timeline`) are used by the `%If` directive to control whether or not parts of a specification are processed or ignored.

Platforms are mutually exclusive - only one platform can be enabled at a time. By default all platforms are disabled. The `tags` value of the bindings section in `pyproject.toml` is used to enable a platform.

If a platform is enabled then SIP will automatically generate a corresponding C preprocessor symbol for use by handwritten code. The symbol is the name of the platform prefixed by `SIP_PLATFORM_`.

For example:

    %Platforms {WIN32_PLATFORM POSIX_PLATFORM MACOS_PLATFORM}

    %If (WIN32_PLATFORM)
    void undocumented();
    %End

    %If (POSIX_PLATFORM)
    void documented();
    %End

## `%PostInitialisationCode`

    %PostInitialisationCode
        code
    %End

This directive is used to specify handwritten code that is embedded in-line at the very end of the generated module initialisation code.

The following variables are made available to the handwritten code:

PyObject *sipModule

  This is the module object returned by `Py_InitModule()`.

PyObject *sipModuleDict

  This is the module’s dictionary object returned by `Py_ModuleGetDict()`.

For example:

    %PostInitialisationCode
        // The code will be executed when the module is first imported and
        // after all other initialisation has been completed.
    %End

## `%PreInitialisationCode`

    %PreInitialisationCode
        code
    %End

This directive is used to specify handwritten code that is embedded in-line at the very start of the generated module initialisation code.

For example:

    %PreInitialisationCode
        // The code will be executed when the module is first imported and
        // before other initialisation has been completed.
    %End

## `%Property`

    %Property(name = name, get = name [, set = name])
    {
        [%Docstring]
    };

This directive is used to define a Python property. `name` is the name of the property.

`get` is the Python name of the getter method and must refer to a method in the same class.

`set` is the Python name of the optional setter method and must refer to a method in the same class.

The optional `%Docstring` sub-directive is used to specify the property’s docstring.

For example:

    class Klass
    {
    public:
        int get_count() const;
        void set_count();

        %Property(name=count, get=get_count, set=set_count)
    };

## `%PreMethodCode`

    %PreMethodCode
        code
    %End

This directive is used as part of the specification of a global function, class method, operator, constructor or destructor to specify handwritten code that is inserted before the default code for calling the wrapped function, or before the `%MethodCode` directive if it is also given.

## `%RaiseCode`

    %RaiseCode
        code
    %End

This directive is used as part of the definition of an exception using the `%Exception` directive to specify handwritten code that raises a Python exception when a C++ exception has been caught. The code is embedded in-line as the body of a C++ `catch ()` clause.

The specified code must handle the Python Global Interpreter Lock (GIL) if necessary. The GIL must be acquired before any calls to the Python API and released after the last call as shown in this example fragment:

    SIP_BLOCK_THREADS
    PyErr_SetNone(PyErr_Exception);
    SIP_UNBLOCK_THREADS

Finally, the specified code must not include any `return` statements.

The following variable is made available to the handwritten code:

type &sipExceptionRef

  This is a reference to the caught C++ exception.

See the `%Exception` directive for an example.

## `%ReleaseCode`

    %ReleaseCode
        code
    %End

This directive is used to specify handwritten code that releases a C/C++ instance to the heap. By default a C instance is released by calling `sipFree()` and a C++ instance is released by calling its destructor. It is specified as part of the `%MappedType` directive.

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the C/C++ instance.

int sipState

  This is the value of the `SIP_USER` returned by the code specified by the corresponding `%ConvertToTypeCode` directive.

void *sipUserState

  This is the value of the pointer saved by the code specified by the corresponding `%ConvertToTypeCode` directive.

## `%SetCode`

    %SetCode
        code
    %End

This sub-directive is used in the declaration of a C++ class variable or C structure member to specify handwritten code to convert it from a Python object. It is usually used to handle types that SIP cannot deal with automatically.

The following variables are made available to the handwritten code:

type *sipCpp

  This is a pointer to the structure or class instance. Its type is a pointer to the structure or class. It is not made available if the variable being wrapped is a static class variable.

int sipErr

  If the conversion failed then the handwritten code should raise a Python exception and set this to a non-zero value. Its initial value will be automatically set to zero.

PyObject *sipPy

  This is the Python object that the handwritten code should convert.

PyObject *sipPyType

  If the variable being wrapped is a static class variable then this is the Python type object of the class from which the variable was referenced (not the class in which it is defined). It may be safely cast to a PyTypeObject * or a sipWrapperType *.

See also

`%AccessCode`, `%GetCode`

## `%Timeline`

    %Timeline {name name ...}

This directive is used to declare a set of versions released over a period of time. Versions (along with `%Feature` and `%Platforms`) are used by the `%If` directive to control whether or not parts of a specification are processed or ignored.

Versions are mutually exclusive - only one version can be enabled at a time. The `tags` value of the bindings section in `pyproject.toml` is used to enable a version. If a timeline does not have a version explicitly enabled then the latest version will be enabled automatically.

The `%Timeline` directive can be used any number of times in a module to allow multiple libraries to be wrapped in the same module.

SIP automatically defines a timeline containing all versions of SIP. The name of the version is `SIP_` followed by the individual parts of the version number separated by an underscore. SIP v5.0.1 is therefore `SIP_5_0_1`.

If a particular version is enabled then SIP will automatically generate a corresponding C preprocessor symbol for use by handwritten code. The symbol is the name of the version prefixed by `SIP_TIMELINE_`.

For example:

    %Timeline {V1_0 V1_1 V2_0 V3_0}

    %If (V1_0 - V2_0)
    void foo();
    %End

    %If (V2_0 -)
    void foo(int = 0);
    %End

    %If (- SIP_4_13)
    void bar();
    %End

## `%TypeCode`

    %TypeCode
        code
    %End

This directive is used as part of the specification of a C structure, a C++ class or a `%MappedType` directive to specify handwritten code, typically the implementations of utility functions, that can be called by other handwritten code in the structure or class.

For example:

    class Klass
    {
    %TypeCode
    // Print an instance on stderr for debugging purposes.
    static void dump_klass(const Klass *k)
    {
        fprintf(stderr,"Klass %s at %p\n", k->name(), k);
    }
    %End

        // The rest of the class specification.

    };

Because the scope of the code is normally within the generated file that implements the type, any utility functions would normally be declared `static`. However a naming convention should still be adopted to prevent clashes of function names within a module in case the SIP `-j` command line option is used.

## `%TypeHeaderCode`

    %TypeHeaderCode
        code
    %End

This directive is used to specify handwritten code that defines the interface to a C or C++ type being wrapped, either a structure, a class, or a template. It is used within a class definition or a `%MappedType` directive.

Normally code will be a pre-processor `#include` statement.

For example:

    // Wrap the Klass class.
    class Klass
    {
    %TypeHeaderCode
    #include <klass.h>
    %End

        // The rest of the class specification.
    };

## `%TypeHintCode`

    %TypeHintCode
        code
    %End

This directive is used, in the context of a module or an individual class, to specify handwritten code, typically the import of additional modules, that is placed in the PEP 484 type hint stub file for the module or class.

See also

`%ExportedTypeHintCode`

## `%UnitCode`

    %UnitCode
        code
    %End

This directive is used to specify handwritten code that is included at the very start of a generated compilation unit (ie. C or C++ source file). It is typically used to `#include` a C++ precompiled header file.

## `%UnitPostIncludeCode`

    %UnitPostIncludeCode
        code
    %End

This directive is used to specify handwritten code that is included following the `#include` of all header files in a generated compilation unit (ie. C or C++ source file).

## `%VirtualCallCode`

    %VirtualCallCode
        code
    %End

For most classes there are corresponding generated derived classes that contain reimplementations of the class’s virtual methods. These methods (which SIP calls catchers) determine if there is a corresponding Python reimplementation and call it if so. If there is no Python reimplementation then the method in the original class is called instead.

This directive is used to specify handwritten code that replaces the normally generated call to the original class method if there is no Python reimplementation.

The following variables are made available to the handwritten code in the context of a method:

type a0

  There is a variable for each argument of the C++ signature named `a0`, `a1`, etc. If `use_argument_names` has been set in the `%Module` directive then the name of the argument is the real name. The type of the variable is the same as the type defined in the specification.

type sipRes

  The handwritten code should set this to any result to be returned. The type of the variable is the same as the type defined in the C++ signature in the specification.

## `%VirtualCatcherCode`

    %VirtualCatcherCode
        code
    %End

This directive is used to specify handwritten code that replaces the normally generated call to the Python reimplementation of a virtual method and the handling of any returned results. It is usually used to handle argument types and results that SIP cannot deal with automatically.

This directive can also be used in the context of a class destructor to specify handwritten code that is embedded in-line in the internal derived class’s destructor.

In the context of a method the Python Global Interpreter Lock (GIL) is automatically acquired before the specified code is executed and automatically released afterwards.

In the context of a destructor the specified code must handle the GIL. The GIL must be acquired before any calls to the Python API and released after the last call as shown in this example fragment:

    SIP_BLOCK_THREADS
    Py_DECREF(obj);
    SIP_UNBLOCK_THREADS

The following variables are made available to the handwritten code in the context of a method:

type a0

  There is a variable for each argument of the C++ signature named `a0`, `a1`, etc. If `use_argument_names` has been set in the `%Module` directive then the name of the argument is the real name. The type of the variable is the same as the type defined in the specification.

int a0Key

  There is a variable for each argument of the C++ signature that has a type where it is important to ensure that the corresponding Python object is not garbage collected too soon. This only applies to output arguments that return `'\0'` terminated strings. The variable would normally be passed to `sipParseResult()` using either the `A` or `B` format characters.

  If `use_argument_names` has been set in the `%Module` directive then the name of the variable is the real name of the argument with `Key` appended.

int sipIsErr

  The handwritten code should set this to a non-zero value, and raise an appropriate Python exception, if an error is detected.

PyObject *sipMethod

  This object is the Python reimplementation of the virtual C++ method. It is normally passed to `sipCallMethod()`.

type sipRes

  The handwritten code should set this to any result to be returned. The type of the variable is the same as the type defined in the C++ signature in the specification.

int sipResKey

  This variable is only made available if the result has a type where it is important to ensure that the corresponding Python object is not garbage collected too soon. This only applies to `'\0'` terminated strings. The variable would normally be passed to `sipParseResult()` using either the `A` or `B` format characters.

sipSimpleWrapper *sipPySelf

  This variable is only made available if either the `a0Key` or `sipResKey` are made available. It defines the context within which keys are unique. The variable would normally be passed to `sipParseResult()` using the `S` format character.

No variables are made available in the context of a destructor.

For example:

    class Klass
    {
    public:
        virtual int foo(SIP_PYTUPLE) [int (int *)];
    %MethodCode
            // The C++ API takes a 2 element array of integers but passing a
            // two element tuple is more Pythonic.

            int iarr[2];

            if (PyArg_ParseTuple(a0, "ii", &iarr[0], &iarr[1]))
            {
                Py_BEGIN_ALLOW_THREADS
                sipRes = sipCpp->Klass::foo(iarr);
                Py_END_ALLOW_THREADS
            }
            else
            {
                // PyArg_ParseTuple() will have raised the exception.
                sipIsErr = 1;
            }
    %End
    %VirtualCatcherCode
            // Convert the 2 element array of integers to the two element
            // tuple.

            PyObject *result;

            result = sipCallMethod(&sipIsErr, sipMethod, "ii", a0[0], a0[1]);

            if (result != NULL)
            {
                // Convert the result to the C++ type.
                sipParseResult(&sipIsErr, sipMethod, result, "i", &sipRes);

                Py_DECREF(result);
            }
    %End
    };

## `%VirtualErrorHandler`

    %VirtualErrorHandler(name = name)
        code
    %End

This directive is used to define the handwritten code that implements a handler that is called when a Python re-implementation of a virtual C++ function raises a Python exception. If a virtual C++ function does not have a handler the `PyErr_Print()` function is called.

The handler is called after all tidying up has been completed, with the Python Global Interpreter Lock (GIL) held and from the thread that raised the exception. If the handler wants to change the execution path by, for example, throwing a C++ exception, it must first release the GIL by calling `SIP_RELEASE_GIL()`. It must not call `SIP_RELEASE_GIL()` if the execution path is not changed.

The following variables are made available to the handwritten code:

sipSimpleWrapper *sipPySelf

  This is the class instance containing the Python reimplementation.

sip_gilstate_t sipGILState

  This is an opaque value that must be passed to `SIP_RELEASE_GIL()` in order to release the GIL prior to changing the execution path.

For example:

    %VirtualErrorHandler my_handler
        PyObject *exception, *value, *traceback;

        PyErr_Fetch(&exception, &value, &traceback);

        SIP_RELEASE_GIL(sipGILState);

        throw my_exception(sipPySelf, exception, value, traceback);
    %End

See also

`NoVirtualErrorHandler`, `VirtualErrorHandler`, `VirtualErrorHandler`