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.

Some directives have arguments or contain blocks of code or documentation. In the following descriptions these 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 directive is used immediately after 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

%API¶

New in version 4.9.

%API name version

This directive is used to define an API and set its default version number. A version number must be greater than or equal to 1.

See Managing Incompatible APIs for more detail.

For example:

%API PyTQt4 1

%BIGetBufferCode¶

%BIGetBufferCode
    code
%End

This directive (along with %BIReleaseBufferCode) is used to specify code that implements the buffer interface of Python v3. If Python v2 is being used then this is ignored.

The following variables are made available to the handwritten code:

Py_buffer *sipBuffer: This is a pointer to the Python buffer structure that the handwritten code must populate.
type *sipCpp: This is a pointer to the structure or class instance. Its type is a pointer to the structure or class.
int sipFlags: 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.

%BIGetCharBufferCode¶

%BIGetCharBufferCode
    code
%End

This directive (along with %BIGetReadBufferCode, %BIGetSegCountCode and %BIGetWriteBufferCode) is used to specify code that implements the buffer interface of Python v2. If Python v3 is being used then this is ignored.

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.
void **sipPtrPtr: This is the pointer used to return the address of the character buffer.
SIP_SSIZE_T sipRes: The handwritten code should set this to the length of the character buffer or -1 if there was an error.
SIP_SSIZE_T sipSegment: This is the number of the segment of the character buffer.
PyObject *sipSelf: This is the Python object that wraps the structure or class instance, i.e. self.

%BIGetReadBufferCode¶

%BIGetReadBufferCode
    code
%End

This directive (along with %BIGetCharBufferCode, %BIGetSegCountCode and %BIGetWriteBufferCode) is used to specify code that implements the buffer interface of Python v2. If Python v3 is being used then this is ignored.

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.
void **sipPtrPtr: This is the pointer used to return the address of the read buffer.
SIP_SSIZE_T sipRes: The handwritten code should set this to the length of the read buffer or -1 if there was an error.
SIP_SSIZE_T sipSegment: This is the number of the segment of the read buffer.
PyObject *sipSelf: This is the Python object that wraps the structure or class instance, i.e. self.

%BIGetSegCountCode¶

%BIGetSegCountCode
    code
%End

This directive (along with %BIGetCharBufferCode, %BIGetReadBufferCode and %BIGetWriteBufferCode) is used to specify code that implements the buffer interface of Python v2. If Python v3 is being used then this is ignored.

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.
SIP_SSIZE_T *sipLenPtr: This is the pointer used to return the total length in bytes of all segments of the buffer.
SIP_SSIZE_T sipRes: The handwritten code should set this to the number of segments that make up the buffer.
PyObject *sipSelf: This is the Python object that wraps the structure or class instance, i.e. self.

%BIGetWriteBufferCode¶

%BIGetWriteBufferCode
    code
%End

This directive (along with %BIGetCharBufferCode, %BIGetReadBufferCode and %BIGetSegCountCode is used to specify code that implements the buffer interface of Python v2. If Python v3 is being used then this is ignored.

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.
void **sipPtrPtr: This is the pointer used to return the address of the write buffer.
SIP_SSIZE_T sipRes: The handwritten code should set this to the length of the write buffer or -1 if there was an error.
SIP_SSIZE_T sipSegment: This is the number of the segment of the write buffer.
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 the buffer interface of Python v3. If Python v2 is being used then this is ignored.

The following variables are made available to the handwritten code:

Py_buffer *sipBuffer: 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.

%CModule¶

%CModule name [version]

This directive is used to identify that the library being wrapped is a C library and to define the name of the module and it’s optional version number.

See the %Module directive for an explanation of the version number.

For example:

%CModule dbus 1

%CompositeModule¶

%CompositeModule name

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 %CModule or %Module directive is interpreted as defining a component module.

For example:

%CompositeModule PyTQt4.TQt
%Include TQtCore/TQtCoremod.sip
%Include TQtGui/TQtGuimod.sip

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

%ConsolidatedModule¶

%ConsolidatedModule name

A consolidated module is one that consolidates the wrapper code of a number of SIP generated modules (refered to as component modules in this context).

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

For example:

%ConsolidatedModule PyTQt4._qt
%Include TQtCore/TQtCoremod.sip
%Include TQtGui/TQtGuimod.sip

A consolidated module is not intended to be explicitly imported by an application. Instead it is imported by its component modules when they themselves are imported.

Normally the wrapper code is contained in the component module and is linked against the corresponding C or C++ library. The advantage of a consolidated module is that it allows all of the wrapped C or C++ libraries to be linked against a single module. If the linking is done statically then deployment of generated modules can be greatly simplified.

It follows that a component module can be built in one of two ways, as a normal standalone module, or as a component of a consolidated module. When building as a component the -p command line option should be used to specify the name of the consolidated module.

%ConvertFromTypeCode¶

%ConvertFromTypeCode
    code
%End

This directive is used as part of the %MappedType directive to specify the handwritten code that converts an instance of a mapped type to a Python object.

The following variables are made available to the handwritten code:

type *sipCpp: This is a pointer to the instance of the mapped type 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 TQPtrList<TQWidget *> instance to a Python list of TQWidget 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 TQWidget.
    for (int i = 0; i < sipCpp->size(); ++i)
    {
        TQWidget *w = sipCpp->at(i);
        PyObject *wobj;

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

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

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

%ConvertToSubClassCode¶

%ConvertToSubClassCode
    code
%End

When SIP needs to wrap a C++ class instance it first checks to make sure it hasn’t already done so. If it has then it just returns a new reference to the corresponding Python object. Otherwise it creates a new Python object of the appropriate type. In C++ a function may be defined to return an instance of a certain class, but can often return a sub-class instead.

This directive is used to specify handwritten code that exploits any available real-time type information (RTTI) to see if there is a more specific Python type that can be used when wrapping the C++ instance. The RTTI may be provided by the compiler or by the C++ instance itself.

The directive is included in the specification of one of the classes that the handwritten code handles the type conversion for. It doesn’t matter which one, but a sensible choice would be the one at the root of that class hierarchy in the module.

Note that if a class hierarchy extends over a number of modules then this directive should be used in each of those modules to handle the part of the hierarchy defined in that module. SIP will ensure that the different pieces of code are called in the right order to determine the most specific Python type to use.

The following variables are made available to the handwritten code:

type *sipCpp

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

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.

sipWrapperType *sipClass

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

This is deprecated from SIP v4.8. Instead you should use sipType.

The handwritten code must not explicitly return.

The following example shows the sub-class conversion code for TQEvent based class hierarchy in PyTQt:

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

    case TQEvent::KeyPress:
    case TQEvent::KeyRelease:
        sipType = sipType_TQKeyEvent;
        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 mapped type 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. For example, PyTQt uses it in the specification of the TQString class to allow Python string objects and unicode objects to be used wherever TQString instances are expected.

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.

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 to avoid a memory leak.

SIP_DERIVED_CLASS is set to indicate that the type of the returned instance is a derived class. See Generated Derived Classes.

The following example converts a Python list of TQPoint instances to a TQPtrList<TQPoint> 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.
        if (!PyList_Check(sipPy))
            return 0;

        // Check the type of each element.  We specify SIP_NOT_NONE to
        // disallow None because it is a list of TQPoint, not of a pointer
        // to a TQPoint, so None isn't appropriate.
        for (int i = 0; i < PyList_GET_SIZE(sipPy); ++i)
            if (!sipCanConvertToType(PyList_GET_ITEM(sipPy, i),
                                     sipType_TQPoint, SIP_NOT_NONE))
                return 0;

        // The type is valid.
        return 1;
    }

    // Create the instance on the heap.
    TQPtrList<TQPoint> *ql = new TQPtrList<TQPoint>;

    for (int i = 0; i < PyList_GET_SIZE(sipPy); ++i)
    {
        TQPoint *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<TQPoint *>(sipConvertToType(
                                                PyList_GET_ITEM(sipPy, i),
                                                sipType_TQPoint, 0,
                                                SIP_NOT_NONE,
                                                &state, sipIsErr));

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

            // Tidy up.
            delete ql;

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

        ql->append(*qp);

        // A copy of the TQPoint 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_TQPoint, 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 sipConvertToType() to convert the object. The SIP_NO_CONVERTORS flag must be passed to both 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) 2009 Riverbank Computing Limited
%End

%DefaultEncoding¶

%DefaultEncoding string

This directive is used to specify the default encoding used for char, const char, char * or const char * values. The encoding can be either "ASCII", "Latin-1", "UTF-8" or "None". 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 "None" is used.

For example:

%DefaultEncoding "Latin-1"

%DefaultMetatype¶

%DefaultMetatype 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 PyTQt4.TQtCore.pytqtWrapperType

%DefaultSupertype¶

%DefaultSupertype 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

%Doc¶

%Doc
    text
%End

This directive is used to specify some arbitrary text that will be extracted by SIP when the -d command line option is used. The directive can be specified any number of times and SIP will concatenate all the separate pieces of text in the order that it sees them.

Documentation that is specified using this directive is local to the module in which it appears. It is ignored by modules that %Import it. Use the %ExportedDoc directive for documentation that should be included by all modules that %Import this one.

For example:

%Doc
<h1>An Example</h1>
<p>
This fragment of documentation is HTML and is local to the module in
which it is defined.
</p>
%End

%Docstring¶

%Docstring
    text
%End

New in version 4.10.

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

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.

Specifying an explicit docstring will prevent SIP from generating an automatic docstring that describes the Python signature of a function or method overload. This means 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.

For example:

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

public:
    Klass();
%Docstring
This will be appended to the class's docstring.
%End
};

%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)]
{
    [*header-code]
    raise-code
};

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 throw () specifiers must either be names of classes or the names of Python exceptions defined by this directive.

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.

header-code is the optional %TypeHeaderCode used to specify any external interface to the exception being defined.

raise-code is the %RaiseCode 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.

%ExportedDoc¶

%ExportedDoc
    text
%End

This directive is used to specify some arbitrary text that will be extracted by SIP when the -d command line option is used. The directive can be specified any number of times and SIP will concatenate all the separate pieces of text in the order that it sees them.

Documentation that is specified using this directive will also be included by modules that %Import it.

For example:

%ExportedDoc
==========
An Example
==========

This fragment of documentation is reStructuredText and will appear in the
module in which it is defined and all modules that %Import it.
%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 and %ModuleHeaderCode.

%Feature¶

%Feature 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 disable. By default all features are enabled. The SIP -x command line option is used to disable a feature.

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

%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 Embedding and Extending the Python Interpreter 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 PyTQt. The TQCustomEvent class allows arbitary data to be attached to the event. In PyTQt 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 PyTQt’s TQCustomEvent 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 directive is used after 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
}

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

Note that this directive is not implemented as a preprocessor. Only the following parts of a specification are affected by it:

%API

class

%ConvertFromTypeCode

%ConvertToSubClassCode

%ConvertToTypeCode

enum

%DefaultEncoding

%DefaultMetatype

%DefaultSupertype

%ExportedHeaderCode

functions

%GCClearCode

%GCTraverseCode

%If

%InitialisationCode

%MappedType

%MethodCode

%ModuleCode

%ModuleHeaderCode

namespace

%PostInitialisationCode

%PreInitialisationCode

struct

typedef

%TypeCode

%TypeHeaderCode

%UnitCode

variables

%VirtualCatcherCode

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

%Import¶

%Import 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 filename cannot be opened then SIP prepends filename 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 filename with each of the directories, in turn, specified by the -I command line option.

For example:

%Import tqt/tqtmod.sip

%Include¶

%Include filename

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 %Import when trying to open filename.

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

%License¶

%License /license-annotations/

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. The elements of the dictionary are specified using the Licensee, Signature, Timestamp and Type annotations. Only the Type annotation is compulsory.

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 /Type="GPL"/

%MappedType¶

template<type-list>
%MappedType type
{
    [header-code]
    [convert-to-code]
    [convert-from-code]
};

%MappedType type
{
    [header-code]
    [convert-to-code]
    [convert-from-code]
};

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.

header-code is the %TypeHeaderCode used to specify the library interface to the type being mapped.

convert-to-code is the %ConvertToTypeCode used to specify the handwritten code that converts a Python object to an instance of the mapped type.

convert-from-code is the %ConvertFromTypeCode used to specify the handwritten code that converts an instance of the mapped type to a Python object.

For example:

template<Type *>
%MappedType TQPtrList
{
%TypeHeaderCode
// Include the library interface to the type being mapped.
#include <qptrlist.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.
    TQPtrList<Type *> *ql = new TQPtrList<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_SetItem(l, i, tobj);
    }

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

Using this we can use, for example, TQPtrList<TQObject *> 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 TQObject 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. 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.

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 sipErrorFail1 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 method then this is the Python object that wraps the structure or class instance, i.e. self.

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 [version]

This directive is used to identify that the library being wrapped is a C++ library and to define the name of the module and it’s optional version number.

The name may contain periods to specify that the module is part of a Python package.

The optional version number is useful if you (or others) might create other modules that build on this module, i.e. if another module might %Import this module. Under the covers, a module exports an API that is used by modules that %Import it and the API is given a version number. A module built on that module knows the version number of the API that it is expecting. If, when the modules are imported at run-time, the version numbers do not match then a Python exception is raised. The dependent module must then be re-built using the correct specification files for the base module.

The version number should be incremented whenever a module is changed. Some changes don’t affect the exported API, but it is good practice to change the version number anyway.

For example:

%Module tqt 5

%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

%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 and %ModuleCode.

%OptionalInclude¶

%OptionalInclude filename

This directive is identical to the %Include directive except that SIP silently continues processing if filename could not be opened.

For example:

%OptionalInclude license.sip

%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 SIP -t command line option is used to enable a 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

%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. The type of the reference is the same as the type defined in the throw () specifier.

See the %Exception directive for an example.

%SetCode¶

%SetCode
    code
%End

This directive is used after 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 the %GetCode directive for an example.

%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. By default all versions are disabled. The SIP -t command line option is used to enable a version.

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

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

%TypeCode¶

%TypeCode
    code
%End

This directive is used as part of the specification of a C structure or a C++ class 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.
};

%UnitCode¶

%UnitCode
    code
%End

This directive is used to specify handwritten code that it 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.

%VirtualCatcherCode¶

%VirtualCatcherCode
    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 Python reimplementation 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. 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.
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 the 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
};

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