SIP Specification Files ======================= A SIP specification consists of some C/C++ type and function declarations and some directives. The declarations may contain annotations which provide SIP with additional information that cannot be expressed in C/C++. SIP does not include a full C/C++ parser. It is important to understand that a SIP specification describes the Python API, i.e. the API available to the Python programmer when they ``import`` the generated module. It does not have to accurately represent the underlying C/C++ library. There is nothing wrong with omitting functions that make little sense in a Python context, or adding functions implemented with handwritten code that have no C/C++ equivalent. It is even possible (and sometimes necessary) to specify a different super-class hierarchy for a C++ class. All that matters is that the generated code compiles properly. In most cases the Python API matches the C/C++ API. In some cases handwritten code (see :directive:`%MethodCode`) is used to map from one to the other without SIP having to know the details itself. However, there are a few cases where SIP generates a thin wrapper around a C++ method or constructor (see :ref:`ref-derived-classes`) and needs to know the exact C++ signature. To deal with these cases SIP allows two signatures to be specified. For example:: class Klass { public: // The Python signature is a tuple, but the underlying C++ signature // is a 2 element array. Klass(SIP_PYTUPLE) [(int *)]; %MethodCode int iarr[2]; if (PyArg_ParseTuple(a0, "ii", &iarr[0], &iarr[1])) { // Note that we use the SIP generated derived class // constructor. Py_BEGIN_ALLOW_THREADS sipCpp = new sipKlass(iarr); Py_END_ALLOW_THREADS } %End }; Syntax Definition ----------------- The following is a semi-formal description of the syntax of a specification file. .. parsed-literal:: *specification* ::= {*module-statement*} *module-statement* ::= [*module-directive* | *statement*] *module-directive* ::= [ :directive:`%API` | :directive:`%CompositeModule` | :directive:`%ConsolidatedModule` | :directive:`%Copying` | :directive:`%DefaultEncoding` | :directive:`%DefaultMetatype` | :directive:`%DefaultSupertype` | :directive:`%ExportedHeaderCode` | :directive:`%Extract` | :directive:`%Feature` | :directive:`%Import` | :directive:`%Include` | :directive:`%InitialisationCode` | :directive:`%License` | :directive:`%MappedType` | :directive:`%Module` | :directive:`%ModuleCode` | :directive:`%ModuleHeaderCode` | :directive:`%OptionalInclude` | :directive:`%Platforms` | :directive:`%PreInitialisationCode` | :directive:`%PostInitialisationCode` | :directive:`%Timeline` | :directive:`%UnitCode` | *mapped-type-template*] *statement* :: [*class-statement* | *function* | *variable*] *class-statement* :: [ :directive:`%If` | *class* | *class-template* | *enum* | *namespace* | *opaque-class* | *operator* | *struct* | *typedef* | *exception*] *class* ::= **class** *name* [**:** *super-classes*] [*class-annotations*] **{** {*class-line*} **};** *super-classes* ::= [**public** | **protected** | **private**] *name* [**,** *super-classes*] *class-line* ::= [ *class-statement* | :directive:`%BIGetBufferCode` | :directive:`%BIGetReadBufferCode` | :directive:`%BIGetWriteBufferCode` | :directive:`%BIGetSegCountCode` | :directive:`%BIGetCharBufferCode` | :directive:`%BIReleaseBufferCode` | :directive:`%ConvertToSubClassCode` | :directive:`%ConvertToTypeCode` | :directive:`%Docstring` | :directive:`%GCClearCode` | :directive:`%GCTraverseCode` | :directive:`%InstanceCode` | :directive:`%PickleCode` | :directive:`%TypeCode` | :directive:`%TypeHeaderCode` | *constructor* | *destructor* | *method* | *static-method* | *virtual-method* | *special-method* | *operator* | *virtual-operator* | *class-variable* | **public:** | **public Q_SLOTS:** | **public slots:** | **protected:** | **protected Q_SLOTS:** | **protected slots:** | **private:** | **private Q_SLOTS:** | **private slots:** | **Q_SIGNALS:** | **signals:**] *constructor* ::= [**explicit**] *name* **(** [*argument-list*] **)** [*exceptions*] [*function-annotations*] [*c++-constructor-signature*] **;** [:directive:`%Docstring`] [:directive:`%MethodCode`] *c++-constructor-signature* ::= **[(** [*argument-list*] **)]** *destructor* ::= [**virtual**] **~** *name* **()** [*exceptions*] [**= 0**] [*function-annotations*] **;** [:directive:`%MethodCode`] [:directive:`%VirtualCatcherCode`] *method* ::= [**Q_SIGNAL**] [**Q_SLOT**] *type* *name* **(** [*argument-list*] **)** [**const**] [*exceptions*] [**= 0**] [*function-annotations*] [*c++-signature*] **;** [:directive:`%Docstring`] [:directive:`%MethodCode`] *c++-signature* ::= **[** *type* **(** [*argument-list*] **)]** *static-method* ::= **static** *function* *virtual-method* ::= [**Q_SIGNAL**] [**Q_SLOT**] **virtual** *type* *name* **(** [*argument-list*] **)** [**const**] [*exceptions*] [**= 0**] [*function-annotations*] [*c++-signature*] **;** [:directive:`%MethodCode`] [:directive:`%VirtualCatcherCode`] *special-method* ::= *type* *special-method-name* **(** [*argument-list*] **)** [*function-annotations*] **;** [:directive:`%MethodCode`] *special-method-name* ::= [**__abs__** | **__add__** | **__and__** | **__bool__** | **__call__** | **__cmp__** | **__contains__** | **__delattr__** | **__delitem__** | **__div__** | **__eq__** | **__float__** | **__floordiv__** | **__ge__** | **__getattr__** | **__getattribute__** | **__getitem__** | **__gt__** | **__hash__** | **__iadd__** | **__iand__** | **__idiv__** | **__ifloordiv__** | **__ilshift__** | **__imod__** | **__imul__** | **__index__** | **__int__** | **__invert__** | **__ior__** | **__irshift__** | **__isub__** | **__iter__** | **__itruediv__** | **__ixor__** | **__le__** | **__len__** | **__long__** | **__lshift__** | **__lt__** | **__mod__** | **__mul__** | **__ne__** | **__neg__** | **__next__** | **__nonzero__** | **__or__** | **__pos__** | **__repr__** | **__rshift__** | **__setattr__** | **__setitem__** | **__str__** | **__sub__** | **__truediv__** | **__xor__**] *operator* ::= *operator-type* **(** [*argument-list*] **)** [**const**] [*exceptions*] [*function-annotations*] **;** [:directive:`%MethodCode`] *virtual-operator* ::= **virtual** *operator-type* **(** [*argument-list*] **)** [**const**] [*exceptions*] [**= 0**] [*function-annotations*] **;** [:directive:`%MethodCode`] [:directive:`%VirtualCatcherCode`] *operatator-type* ::= [ *operator-function* | *operator-cast* ] *operator-function* ::= *type* **operator** *operator-name* *operator-cast* ::= **operator** *type* *operator-name* ::= [**+** | **-** | ***** | **/** | **%** | **&** | **|** | **^** | **<<** | **>>** | **+=** | **-=** | ***=** | **/=** | **%=** | **&=** | **|=** | **^=** | **<<=** | **>>=** | **~** | **()** | **[]** | **<** | **<=** | **==** | **!=** | **>** | **>>=** | **=**] *class-variable* ::= [**static**] *variable* *class-template* :: = **template** **<** *type-list* **>** *class* *mapped-type-template* :: = **template** **<** *type-list* **>** :directive:`%MappedType` *enum* ::= **enum** [*name*] [*enum-annotations*] **{** {*enum-line*} **};** *enum-line* ::= [:directive:`%If` | *name* [*enum-annotations*] **,** *function* ::= *type* *name* **(** [*argument-list*] **)** [*exceptions*] [*function-annotations*] **;** [:directive:`%Docstring`] [:directive:`%MethodCode`] *namespace* ::= **namespace** *name* [**{** {*namespace-line*} **}**] **;** *namespace-line* ::= [:directive:`%TypeHeaderCode` | *statement*] *opaque-class* ::= **class** *scoped-name* **;** *struct* ::= **struct** *name* **{** {*class-line*} **};** *typedef* ::= **typedef** [*typed-name* | *function-pointer*] *typedef-annotations* **;** *variable*::= *typed-name* [*variable-annotations*] **;** [:directive:`%AccessCode`] [:directive:`%GetCode`] [:directive:`%SetCode`] *exception* ::= :directive:`%Exception` *exception-name* [*exception-base*] **{** [:directive:`%TypeHeaderCode`] :directive:`%RaiseCode` **};** *exception-name* ::= *scoped-name* *exception-base* ::= **(** [*exception-name* | *python-exception*] **)** *python-exception* ::= [**SIP_Exception** | **SIP_StopIteration** | **SIP_StandardError** | **SIP_ArithmeticError** | **SIP_LookupError** | **SIP_AssertionError** | **SIP_AttributeError** | **SIP_EOFError** | **SIP_FloatingPointError** | **SIP_EnvironmentError** | **SIP_IOError** | **SIP_OSError** | **SIP_ImportError** | **SIP_IndexError** | **SIP_KeyError** | **SIP_KeyboardInterrupt** | **SIP_MemoryError** | **SIP_NameError** | **SIP_OverflowError** | **SIP_RuntimeError** | **SIP_NotImplementedError** | **SIP_SyntaxError** | **SIP_IndentationError** | **SIP_TabError** | **SIP_ReferenceError** | **SIP_SystemError** | **SIP_SystemExit** | **SIP_TypeError** | **SIP_UnboundLocalError** | **SIP_UnicodeError** | **SIP_UnicodeEncodeError** | **SIP_UnicodeDecodeError** | **SIP_UnicodeTranslateError** | **SIP_ValueError** | **SIP_ZeroDivisionError** | **SIP_WindowsError** | **SIP_VMSError**] *exceptions* ::= **throw (** [*exception-list*] **)** *exception-list* ::= *scoped-name* [**,** *exception-list*] *argument-list* ::= *argument* [**,** *argument-list*] [**,** **...**] *argument* ::= [ *type* [*name*] [*argument-annotations*] [*default-value*] | :stype:`SIP_ANYSLOT` [*default-value*] | :stype:`SIP_QOBJECT` | :stype:`SIP_RXOBJ_CON` | :stype:`SIP_RXOBJ_DIS` | :stype:`SIP_SIGNAL` [*default-value*] | :stype:`SIP_SLOT` [*default-value*] | :stype:`SIP_SLOT_CON` | :stype:`SIP_SLOT_DIS` | :stype:`SIP_SSIZE_T`] *default-value* ::= **=** *expression* *expression* ::= [*value* | *value* *binary-operator* *expression*] *value* ::= [*unary-operator*] *simple-value* *simple-value* ::= [*scoped-name* | *function-call* | *real-value* | *integer-value* | *boolean-value* | *string-value* | *character-value*] *typed-name*::= *type* *name* *function-pointer*::= *type* **(*** *name* **)(** [*type-list*] **)** *type-list* ::= *type* [**,** *type-list*] *function-call* ::= *scoped-name* **(** [*value-list*] **)** *value-list* ::= *value* [**,** *value-list*] *real-value* ::= a floating point number *integer-value* ::= a number *boolean-value* ::= [**true** | **false**] *string-value* ::= **"** {*character*} **"** *character-value* ::= **'** *character* **'** *unary-operator* ::= [**!** | **~** | **-** | **+** | **\*** | **&**] *binary-operator* ::= [**-** | **+** | ***** | **/** | **&** | **|**] *argument-annotations* ::= see :ref:`ref-arg-annos` *class-annotations* ::= see :ref:`ref-class-annos` *enum-annotations* ::= see :ref:`ref-enum-annos` *function-annotations* ::= see :ref:`ref-function-annos` *typedef-annotations* ::= see :ref:`ref-typedef-annos` *variable-annotations* ::= see :ref:`ref-variable-annos` *type* ::= [**const**] *base-type* {*****} [**&**] *type-list* ::= *type* [**,** *type-list*] *base-type* ::= [*scoped-name* | *template* | **struct** *scoped-name* | **char** | **signed char** | **unsigned char** | **wchar_t** | **int** | **unsigned** | **unsigned int** | **short** | **unsigned short** | **long** | **unsigned long** | **long long** | **unsigned long long** | **float** | **double** | **bool** | **void** | **PyObject** | :stype:`SIP_PYBUFFER` | :stype:`SIP_PYCALLABLE` | :stype:`SIP_PYDICT` | :stype:`SIP_PYLIST` | :stype:`SIP_PYOBJECT` | :stype:`SIP_PYSLICE` | :stype:`SIP_PYTUPLE` | :stype:`SIP_PYTYPE`] *scoped-name* ::= *name* [**::** *scoped-name*] *template* ::= *scoped-name* **<** *type-list* **>** *dotted-name* ::= *name* [**.** *dotted-name*] *name* ::= _A-Za-z {_A-Za-z0-9} Here is a short list of differences between C++ and the subset supported by SIP that might trip you up. - SIP does not support the use of ``[]`` in types. Use pointers instead. - A global ``operator`` can only be defined if its first argument is a class or a named enum that has been wrapped in the same module. - Variables declared outside of a class are effectively read-only. - A class's list of super-classes doesn't not include any access specifier (e.g. ``public``). Variable Numbers of Arguments ----------------------------- SIP supports the use of ``...`` as the last part of a function signature. Any remaining arguments are collected as a Python tuple. Additional SIP Types -------------------- SIP supports a number of additional data types that can be used in Python signatures. .. sip-type:: SIP_ANYSLOT This is both a ``const char *`` and a ``PyObject *`` that is used as the type of the member instead of ``const char *`` in functions that implement the connection or disconnection of an explicitly generated signal to a slot. Handwritten code must be provided to interpret the conversion correctly. .. sip-type:: SIP_PYBUFFER This is a ``PyObject *`` that implements the Python buffer protocol. .. sip-type:: SIP_PYCALLABLE This is a ``PyObject *`` that is a Python callable object. .. sip-type:: SIP_PYDICT This is a ``PyObject *`` that is a Python dictionary object. .. sip-type:: SIP_PYLIST This is a ``PyObject *`` that is a Python list object. .. sip-type:: SIP_PYOBJECT This is a ``PyObject *`` of any Python type. The type ``PyObject *`` can also be used. .. sip-type:: SIP_PYSLICE This is a ``PyObject *`` that is a Python slice object. .. sip-type:: SIP_PYTUPLE This is a ``PyObject *`` that is a Python tuple object. .. sip-type:: SIP_PYTYPE This is a ``PyObject *`` that is a Python type object. .. sip-type:: SIP_QOBJECT This is a ``QObject *`` that is a C++ instance of a class derived from Qt's ``QObject`` class. .. sip-type:: SIP_RXOBJ_CON This is a ``QObject *`` that is a C++ instance of a class derived from Qt's ``QObject`` class. It is used as the type of the receiver instead of ``const QObject *`` in functions that implement a connection to a slot. .. sip-type:: SIP_RXOBJ_DIS This is a ``QObject *`` that is a C++ instance of a class derived from Qt's ``QObject`` class. It is used as the type of the receiver instead of ``const QObject *`` in functions that implement a disconnection from a slot. .. sip-type:: SIP_SIGNAL This is a ``const char *`` that is used as the type of the signal instead of ``const char *`` in functions that implement the connection or disconnection of an explicitly generated signal to a slot. .. sip-type:: SIP_SLOT This is a ``const char *`` that is used as the type of the member instead of ``const char *`` in functions that implement the connection or disconnection of an explicitly generated signal to a slot. .. sip-type:: SIP_SLOT_CON This is a ``const char *`` that is used as the type of the member instead of ``const char *`` in functions that implement the connection of an internally generated signal to a slot. The type includes a comma separated list of types that is the C++ signature of of the signal. To take an example, ``QAccel::connectItem()`` connects an internally generated signal to a slot. The signal is emitted when the keyboard accelerator is activated and it has a single integer argument that is the ID of the accelerator. The C++ signature is:: bool connectItem(int id, const QObject *receiver, const char *member); The corresponding SIP specification is:: bool connectItem(int, SIP_RXOBJ_CON, SIP_SLOT_CON(int)); .. sip-type:: SIP_SLOT_DIS This is a ``const char *`` that is used as the type of the member instead of ``const char *`` in functions that implement the disconnection of an internally generated signal to a slot. The type includes a comma separated list of types that is the C++ signature of of the signal. .. sip-type:: SIP_SSIZE_T This is a ``Py_ssize_t`` in Python v2.5 and later and ``int`` in earlier versions of Python. Classic Division and True Division ---------------------------------- SIP supports the ``__div__`` and ``__truediv__`` special methods (and the corresponding inplace versions) for both Python v2 and v3. For Python v2 the ``__div__`` method will be used for both classic and true division if a ``__truediv__`` method is not defined. For Python v3 the ``__div__`` method will be used for true division if a ``__truediv__`` method is not defined. For all versions of Python, if both methods are defined then ``__div__`` should be defined first. Namespaces ---------- SIP implements C++ namespaces as a Python class which cannot be instantiated. The contents of the namespace, including nested namespaces, are implemented as attributes of the class. The namespace class is created in the module that SIP is parsing when it first sees the namespace defined. If a function (for example) is defined in a namespace that is first defined in another module then the function is added to the namespace class in that other module. Say that we have a file ``a.sip`` that defines a module ``a_module`` as follows:: %Module a_module namespace N { void hello(); }; We also have a file ``b.sip`` that defines a module ``b_module`` as follows:: %Module b_module %Import a.sip namespace N { void bye(); }; When SIP parses ``b.sip`` it first sees the ``N`` namespace defined in module ``a_module``. Therefore it places the ``bye()`` function in the ``N`` Python class in the ``a_module``. It does not create an ``N`` Python class in the ``b_module``. Consequently the following code will call the ``bye()`` function:: import a_module import b_module a_module.N.bye() While this reflects the C++ usage it may not be obvious to the Python programmer who might expect to call the ``bye()`` function using:: import b_module b_module.N.bye() In order to achieve this behavior make sure that the ``N`` namespace is first defined in the ``b_module``. The following version of ``b.sip`` does this:: %Module b_module namespace N; %Import a.sip namespace N { void bye(); }; Alternatively you could just move the :directive:`%Import` directive so that it is at the end of the file.