Object Protocol — Python documentation

Object Protocol

PyObject *Py_NotImplemented

The NotImplemented singleton, used to signal that an operation is not implemented for the given type combination.

Py_RETURN_NOTIMPLEMENTED

Properly handle returning Py_NotImplemented from within a C function (that is, increment the reference count of NotImplemented and return it).

int PyObject_Print(PyObject *o, FILE *fp, int flags)

Print an object o, on file fp. Returns -1 on error. The flags argument is used to enable certain printing options. The only option currently supported is Py_PRINT_RAW; if given, the str() of the object is written instead of the repr().

int PyObject_HasAttr(PyObject *o, PyObject *attr_name)

Returns 1 if o has the attribute attr_name, and 0 otherwise. This is equivalent to the Python expression hasattr(o, attr_name). This function always succeeds.

Note that exceptions which occur while calling __getattr__() and __getattribute__() methods will get suppressed. To get error reporting use PyObject_GetAttr() instead.

int PyObject_HasAttrString(PyObject *o, const char *attr_name)

Returns 1 if o has the attribute attr_name, and 0 otherwise. This is equivalent to the Python expression hasattr(o, attr_name). This function always succeeds.

Note that exceptions which occur while calling __getattr__() and __getattribute__() methods and creating a temporary string object will get suppressed. To get error reporting use PyObject_GetAttrString() instead.

PyObject *PyObject_GetAttr(PyObject *o, PyObject *attr_name)

Retrieve an attribute named attr_name from object o. Returns the attribute value on success, or NULL on failure. This is the equivalent of the Python expression o.attr_name.

PyObject *PyObject_GetAttrString(PyObject *o, const char *attr_name)

Retrieve an attribute named attr_name from object o. Returns the attribute value on success, or NULL on failure. This is the equivalent of the Python expression o.attr_name.

PyObject *PyObject_GenericGetAttr(PyObject *o, PyObject *name)

Generic attribute getter function that is meant to be put into a type object’s tp_getattro slot. It looks for a descriptor in the dictionary of classes in the object’s MRO as well as an attribute in the object’s __dict__ (if present). As outlined in Implementing Descriptors, data descriptors take preference over instance attributes, while non-data descriptors don’t. Otherwise, an AttributeError is raised.

int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)

Set the value of the attribute named attr_name, for object o, to the value v. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o.attr_name = v.

If v is NULL, the attribute is deleted, however this feature is deprecated in favour of using PyObject_DelAttr().

int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)

Set the value of the attribute named attr_name, for object o, to the value v. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o.attr_name = v.

If v is NULL, the attribute is deleted, however this feature is deprecated in favour of using PyObject_DelAttrString().

int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)

Generic attribute setter and deleter function that is meant to be put into a type object’s tp_setattro slot. It looks for a data descriptor in the dictionary of classes in the object’s MRO, and if found it takes preference over setting or deleting the attribute in the instance dictionary. Otherwise, the attribute is set or deleted in the object’s __dict__ (if present). On success, 0 is returned, otherwise an AttributeError is raised and -1 is returned.

int PyObject_DelAttr(PyObject *o, PyObject *attr_name)

Delete attribute named attr_name, for object o. Returns -1 on failure. This is the equivalent of the Python statement del o.attr_name.

int PyObject_DelAttrString(PyObject *o, const char *attr_name)

Delete attribute named attr_name, for object o. Returns -1 on failure. This is the equivalent of the Python statement del o.attr_name.

PyObject *PyObject_GenericGetDict(PyObject *o, void *context)

A generic implementation for the getter of a __dict__ descriptor. It creates the dictionary if necessary.

New in version 3.3.

int PyObject_GenericSetDict(PyObject *o, PyObject *value, void *context)

A generic implementation for the setter of a __dict__ descriptor. This implementation does not allow the dictionary to be deleted.

New in version 3.3.

PyObject *PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)

Compare the values of o1 and o2 using the operation specified by opid, which must be one of Py_LT, Py_LE, Py_EQ, Py_NE, Py_GT, or Py_GE, corresponding to <, <=, ==, !=, >, or >= respectively. This is the equivalent of the Python expression o1 op o2, where op is the operator corresponding to opid. Returns the value of the comparison on success, or NULL on failure.

int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)

Compare the values of o1 and o2 using the operation specified by opid, which must be one of Py_LT, Py_LE, Py_EQ, Py_NE, Py_GT, or Py_GE, corresponding to <, <=, ==, !=, >, or >= respectively. Returns -1 on error, 0 if the result is false, 1 otherwise. This is the equivalent of the Python expression o1 op o2, where op is the operator corresponding to opid.

Note

If o1 and o2 are the same object, PyObject_RichCompareBool() will always return 1 for Py_EQ and 0 for Py_NE.

PyObject *PyObject_Repr(PyObject *o)

Compute a string representation of object o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression repr(o). Called by the repr() built-in function.

Changed in version 3.4: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_ASCII(PyObject *o)

As PyObject_Repr(), compute a string representation of object o, but escape the non-ASCII characters in the string returned by PyObject_Repr() with \x, \u or \U escapes. This generates a string similar to that returned by PyObject_Repr() in Python 2. Called by the ascii() built-in function.

PyObject *PyObject_Str(PyObject *o)

Compute a string representation of object o. Returns the string representation on success, NULL on failure. This is the equivalent of the Python expression str(o). Called by the str() built-in function and, therefore, by the print() function.

Changed in version 3.4: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_Bytes(PyObject *o)

Compute a bytes representation of object o. NULL is returned on failure and a bytes object on success. This is equivalent to the Python expression bytes(o), when o is not an integer. Unlike bytes(o), a TypeError is raised when o is an integer instead of a zero-initialized bytes object.

int PyObject_IsSubclass(PyObject *derived, PyObject *cls)

Return 1 if the class derived is identical to or derived from the class cls, otherwise return 0. In case of an error, return -1.

If cls is a tuple, the check will be done against every entry in cls. The result will be 1 when at least one of the checks returns 1, otherwise it will be 0.

If cls has a __subclasscheck__() method, it will be called to determine the subclass status as described in PEP 3119. Otherwise, derived is a subclass of cls if it is a direct or indirect subclass, i.e. contained in cls.__mro__.

Normally only class objects, i.e. instances of type or a derived class, are considered classes. However, objects can override this by having a __bases__ attribute (which must be a tuple of base classes).

int PyObject_IsInstance(PyObject *inst, PyObject *cls)

Return 1 if inst is an instance of the class cls or a subclass of cls, or 0 if not. On error, returns -1 and sets an exception.

If cls is a tuple, the check will be done against every entry in cls. The result will be 1 when at least one of the checks returns 1, otherwise it will be 0.

If cls has a __instancecheck__() method, it will be called to determine the subclass status as described in PEP 3119. Otherwise, inst is an instance of cls if its class is a subclass of cls.

An instance inst can override what is considered its class by having a __class__ attribute.

An object cls can override if it is considered a class, and what its base classes are, by having a __bases__ attribute (which must be a tuple of base classes).

Py_hash_t PyObject_Hash(PyObject *o)

Compute and return the hash value of an object o. On failure, return -1. This is the equivalent of the Python expression hash(o).

Changed in version 3.2: The return type is now Py_hash_t. This is a signed integer the same size as Py_ssize_t.

Py_hash_t PyObject_HashNotImplemented(PyObject *o)

Set a TypeError indicating that type(o) is not hashable and return -1. This function receives special treatment when stored in a tp_hash slot, allowing a type to explicitly indicate to the interpreter that it is not hashable.

int PyObject_IsTrue(PyObject *o)

Returns 1 if the object o is considered to be true, and 0 otherwise. This is equivalent to the Python expression not not o. On failure, return -1.

int PyObject_Not(PyObject *o)

Returns 0 if the object o is considered to be true, and 1 otherwise. This is equivalent to the Python expression not o. On failure, return -1.

PyObject *PyObject_Type(PyObject *o)

When o is non-NULL, returns a type object corresponding to the object type of object o. On failure, raises SystemError and returns NULL. This is equivalent to the Python expression type(o). This function increments the reference count of the return value. There’s really no reason to use this function instead of the common expression o->ob_type, which returns a pointer of type PyTypeObject*, except when the incremented reference count is needed.

int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)

Return true if the object o is of type type or a subtype of type. Both parameters must be non-NULL.

Py_ssize_t PyObject_Size(PyObject *o)

Py_ssize_t PyObject_Length(PyObject *o)

Return the length of object o. If the object o provides either the sequence and mapping protocols, the sequence length is returned. On error, -1 is returned. This is the equivalent to the Python expression len(o).

Py_ssize_t PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)

Return an estimated length for the object o. First try to return its actual length, then an estimate using __length_hint__(), and finally return the default value. On error return -1. This is the equivalent to the Python expression operator.length_hint(o, defaultvalue).

New in version 3.4.

PyObject *PyObject_GetItem(PyObject *o, PyObject *key)

Return element of o corresponding to the object key or NULL on failure. This is the equivalent of the Python expression o[key].

int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)

Map the object key to the value v. Raise an exception and return -1 on failure; return 0 on success. This is the equivalent of the Python statement o[key] = v. This function does not steal a reference to v.

int PyObject_DelItem(PyObject *o, PyObject *key)

Remove the mapping for the object key from the object o. Return -1 on failure. This is equivalent to the Python statement del o[key].

PyObject *PyObject_Dir(PyObject *o)

This is equivalent to the Python expression dir(o), returning a (possibly empty) list of strings appropriate for the object argument, or NULL if there was an error. If the argument is NULL, this is like the Python dir(), returning the names of the current locals; in this case, if no execution frame is active then NULL is returned but PyErr_Occurred() will return false.

PyObject *PyObject_GetIter(PyObject *o)

This is equivalent to the Python expression iter(o). It returns a new iterator for the object argument, or the object itself if the object is already an iterator. Raises TypeError and returns NULL if the object cannot be iterated.