sip

The main purpose of the sip module is to provide functionality common to all SIP generated bindings. It is loaded automatically and most of the time you will completely ignore it. However, it does expose some functionality that can be used by applications.

class array

This is the type object for the type SIP uses to represent an array of a limited number of C/C++ types. Typically the memory is not owned by Python so that it is not freed when the object is garbage collected. An array object can be created from a voidptr object by calling asarray(). This allows the underlying memory (interpreted as a sequence of unsigned bytes) to be processed much more quickly.

assign(obj, other)

This does the Python equivalent of invoking the assignment operator of a C++ instance (i.e. *obj = other).

Parameters

• obj – the Python object being assigned to.

• other – the Python object being assigned.

cast(obj, type)

This does the Python equivalent of casting a C++ instance to one of its sub or super-class types.

Parameters

• obj – the Python object.

• type (type) – the type.

Returns

a new Python object is that wraps the same C++ instance as obj, but has the type type.

delete(obj)

For C++ instances this calls the C++ destructor. For C structures it returns the structure’s memory to the heap.

Parameters

obj – the Python object.

dump(obj)

This displays various bits of useful information about the internal state of the Python object that wraps a C++ instance or C structure. Note that the reference count that is displayed has the same caveat as that of sys.getrefcount().

Parameters

obj – the Python object.

enableautoconversion(type, enable)

Instances of some classes may be automatically converted to other Python objects even though the class has been wrapped. This allows that behaviour to be suppressed so that an instances of the wrapped class is returned instead. By default it is enabled.

Parameters

• type (type) – the Python type object.

• enable (bool) – is True if auto-conversion should be enabled for the type.

Returns

True or False depending on whether or not auto-conversion was previously enabled for the type. This allows the previous state to be restored later on.

enableoverflowchecking(enable)

This enables or disables the checking for overflows when converting Python integer objects to C/C++ integer types. When it is enabled an exception is raised when the value of a Python integer object is too large to fit in the corresponding C/C++ type. By default it is disabled.

Parameters

enable (bool) – is True if overflow checking should be enabled.

Returns

True or False depending on whether or not overflow checking was previously enabled. This allows the previous state to be restored later on.

isdeleted(obj)

This checks if the C++ instance or C structure has been deleted and returned to the heap.

Parameters

obj – the Python object.

Returns

True if the C/C++ instance has been deleted.

ispycreated(obj)

This checks if the C++ instance or C structure was created by Python. If it was then it is possible to call a C++ instance’s protected methods.

Parameters

obj – the Python object.

Returns

True if the C/C++ instance was created by Python.

ispyowned(obj)

This checks if the C++ instance or C structure is owned by Python.

Parameters

obj – the Python object.

Returns

True if the C/C++ instance is owned by Python.

setdeleted(obj)

This marks the C++ instance or C structure as having been deleted and returned to the heap so that future references to it raise an exception rather than cause a program crash. Normally SIP handles such things automatically, but there may be circumstances where this isn’t possible.

Parameters

obj – the Python object.

setdestroyonexit(destroy)

When the Python interpreter exits it garbage collects those objects that it can. This means that any corresponding C++ instances and C structures owned by Python are destroyed. Unfortunately this happens in an unpredictable order and so can cause memory faults within the wrapped library. Calling this function with a value of False disables the automatic destruction of C++ instances and C structures.

Parameters

destroy (bool) – True if all C++ instances and C structures owned by Python should be destroyed when the interpreter exits. This is the default.

settracemask(mask)

If the bindings have been created with tracing enabled then the generated code will include debugging statements that trace the execution of the code. (It is particularly useful when trying to understand the operation of a C++ library’s virtual function calls.)

Parameters

mask (int) – the mask that determines which debugging statements are enabled.

Debugging statements are generated at the following points:

• in a C++ virtual function (mask is 0x0001)

• in a C++ constructor (mask is 0x0002)

• in a C++ destructor (mask is 0x0004)

• in a Python type’s __init__ method (mask is 0x0008)

• in a Python type’s __del__ method (mask is 0x0010)

• in a Python type’s ordinary method (mask is 0x0020).

By default the trace mask is zero and all debugging statements are disabled.

class simplewrapper

This is an alternative type object than can be used as the base type of an instance wrapped by SIP. Objects using this are smaller than those that use the default wrapper type but do not support the concept of object ownership.

__dtor__()

If the wrapped instance is a C++ class with a virtual destructor then this is called by the destructor.

SIP_VERSION

This is a Python integer object that represents the SIP version number as a 3 part hexadecimal number (e.g. v5.0.0 is represented as 0x050000). Note that it is not the version number of the sip module.

SIP_VERSION_STR

This is a Python string object that defines the SIP version number as represented as a string. For development versions it will contain .dev. Note that it is not the version number of the sip module.

transferback(obj)

This transfers ownership of a C++ instance or C structure to Python.

Parameters

obj – the Python object.

transferto(obj, owner)

This transfers ownership of a C++ instance or C structure to C/C++.

Parameters

• obj – the Python object.

• owner – an optional wrapped instance that obj becomes associated with with regard to the cyclic garbage collector. If owner is None then no such association is made. If owner is the same value as obj then any reference cycles involving obj can never be detected or broken by the cyclic garbage collector. Responsibility for destroying the C++ instance’s destructor or freeing the C structure is always transfered to C/C++.

unwrapinstance(obj)

This returns the address, as an integer, of a wrapped C/C++ structure or class instance.

Parameters

obj – the Python object.

Returns

an integer that is the address of the C/C++ instance.

class voidptr

This is the type object for the type SIP uses to represent a C/C++ void *. It may have a size associated with the address in which case the Python buffer interface is supported. The type has the following methods.

__init__(address, size=-1, writeable=True)

Parameters

• address – the address, either another voidptr, None, a Python Capsule, an object that implements the buffer protocol or an integer.

• size (int) – the optional associated size of the block of memory and is negative if the size is not known.

• writeable (bool) – set if the memory is writeable. If it is not specified, and address is a voidptr instance then its value will be used.

__getitem__(idx)

This returns the item at a given index. An exception will be raised if the address does not have an associated size. In this way it behaves like a Python memoryview object.

Parameters

idx – is the index which may either be an integer, an object that implements __index__() or a slice object.

Returns

the item. If the index is an integer then the item will be a bytes object containing the single byte at that index. If the index is a slice object then the item will be a new voidptr object defining the subset of the memory corresponding to the slice.

__hex__()

This returns the address as a hexadecimal string.

Returns

the hexadecimal string address.

__int__()

This returns the address as an integer.

Returns

the integer address.

__len__()

This returns the size associated with the address.

Returns

the associated size. An exception will be raised if there is none.

__setitem__(idx, item)

This updates the memory at a given index. An exception will be raised if the address does not have an associated size or is not writable. In this way it behaves like a Python memoryview object.

Parameters

• idx – is the index which may either be an integer, an object that implements __index__() or a slice object.

• item – is the data that will update the memory defined by the index. It must implement the buffer interface and be the same size as the data that is being updated.

asarray(size=-1)

This returns the block of memory as an array object. The memory is not copied.

Parameters

size (int) – the size of the array. If it is negative then the size associated with the address is used. If there is no associated size then an exception is raised.

Returns

the array object.

ascapsule()

This returns the address as an unnamed Python Capsule.

Returns

the Capsule.

asstring(size=-1)

This returns a copy of the block of memory as a bytes object.

Parameters

size (int) – the number of bytes to copy. If it is negative then the size associated with the address is used. If there is no associated size then an exception is raised.

Returns

the bytes object.

getsize()

This returns the size associated with the address.

Returns

the associated size which will be negative if there is none.

setsize(size)

This sets the size associated with the address.

Parameters

size (int) – the size to associate. If it is negative then no size is associated.

getwriteable()

This returns the writeable state of the memory.

Returns

True if the memory is writeable.

setwriteable(writeable)

This sets the writeable state of the memory.

Parameters

writeable (bool) – the writeable state to set.

wrapinstance(addr, type)

This wraps a C structure or C++ class instance in a Python object. If the instance has already been wrapped then a new reference to the existing object is returned.

Parameters

• addr (int) – the address of the instance as a number.

• type (type) – the Python type of the instance.

Returns

the Python object that wraps the instance.

class wrapper

This is the type object of the default base type of all instances wrapped by SIP.

class wrappertype

This is the type object of the metatype of the wrapper type.