CPython supports two different calling protocols: tp_call and vectorcall.
Instances of classes that set tp_call are callable. The signature of the slot is:
tp_call
PyObject *tp_call(PyObject *callable, PyObject *args, PyObject *kwargs);
A call is made using a tuple for the positional arguments and a dict for the keyword arguments, similarly to callable(*args, **kwargs) in Python code. args must be non-NULL (use an empty tuple if there are no arguments) but kwargs 可以是 NULL if there are no keyword arguments.
callable(*args, **kwargs)
This convention is not only used by tp_call : tp_new and tp_init also pass arguments this way.
tp_new
tp_init
To call an object, use PyObject_Call() or another call API .
PyObject_Call()
Added in version 3.9.
The vectorcall protocol was introduced in PEP 590 as an additional protocol for making calls more efficient.
As rule of thumb, CPython will prefer the vectorcall for internal calls if the callable supports it. However, this is not a hard rule. Additionally, some third-party extensions use tp_call directly (rather than using PyObject_Call() ). Therefore, a class supporting vectorcall must also implement tp_call . Moreover, the callable must behave the same regardless of which protocol is used. The recommended way to achieve this is by setting tp_call to PyVectorcall_Call() . This bears repeating:
PyVectorcall_Call()
警告
A class supporting vectorcall must also implement tp_call with the same semantics.
Changed in version 3.12: The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a class when the class’s __call__() method is reassigned. (This internally sets tp_call only, and thus may make it behave differently than the vectorcall function.) In earlier Python versions, vectorcall should only be used with immutable or static types.
Py_TPFLAGS_HAVE_VECTORCALL
__call__()
immutable
A class should not implement vectorcall if that would be slower than tp_call . For example, if the callee needs to convert the arguments to an args tuple and kwargs dict anyway, then there is no point in implementing vectorcall.
Classes can implement the vectorcall protocol by enabling the Py_TPFLAGS_HAVE_VECTORCALL flag and setting tp_vectorcall_offset to the offset inside the object structure where a vectorcallfunc appears. This is a pointer to a function with the following signature:
tp_vectorcall_offset
callable is the object being called.
values of the keyword arguments. This can be NULL if there are no arguments.
PY_VECTORCALL_ARGUMENTS_OFFSET flag. To get the actual number of positional arguments from nargsf ，使用 PyVectorcall_NARGS() .
PY_VECTORCALL_ARGUMENTS_OFFSET
PyVectorcall_NARGS()
in other words, the keys of the kwargs dict. These names must be strings (instances of str or a subclass) and they must be unique. If there are no keyword arguments, then kwnames can instead be NULL .
str
If this flag is set in a vectorcall nargsf argument, the callee is allowed to temporarily change args[-1] . In other words, args points to argument 1 (not 0) in the allocated vector. The callee must restore the value of args[-1] before returning.
args[-1]
For PyObject_VectorcallMethod() , this flag means instead that args[0] may be changed.
PyObject_VectorcallMethod()
args[0]
Whenever they can do so cheaply (without additional allocation), callers are encouraged to use PY_VECTORCALL_ARGUMENTS_OFFSET . Doing so will allow callables such as bound methods to make their onward calls (which include a prepended self argument) very efficiently.
Added in version 3.8.
To call an object that implements vectorcall, use a call API function as with any other callable. PyObject_Vectorcall() will usually be most efficient.
PyObject_Vectorcall()
注意
In CPython 3.8, the vectorcall API and related functions were available provisionally under names with a leading underscore: _PyObject_Vectorcall , _Py_TPFLAGS_HAVE_VECTORCALL , _PyObject_VectorcallMethod , _PyVectorcall_Function , _PyObject_CallOneArg , _PyObject_CallMethodNoArgs , _PyObject_CallMethodOneArg . Additionally, PyObject_VectorcallDict was available as _PyObject_FastCallDict . The old names are still defined as aliases of the new, non-underscored names.
_PyObject_Vectorcall
_Py_TPFLAGS_HAVE_VECTORCALL
_PyObject_VectorcallMethod
_PyVectorcall_Function
_PyObject_CallOneArg
_PyObject_CallMethodNoArgs
_PyObject_CallMethodOneArg
PyObject_VectorcallDict
_PyObject_FastCallDict
当使用 tp_call , callees do not need to worry about recursion : CPython uses Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() for calls made using tp_call .
Py_EnterRecursiveCall()
Py_LeaveRecursiveCall()
For efficiency, this is not the case for calls done using vectorcall: the callee should use Py_EnterRecursiveCall and Py_LeaveRecursiveCall 若需要。
Given a vectorcall nargsf argument, return the actual number of arguments. Currently equivalent to:
(Py_ssize_t)(nargsf & ~PY_VECTORCALL_ARGUMENTS_OFFSET)
However, the function PyVectorcall_NARGS should be used to allow for future extensions.
PyVectorcall_NARGS
若 op does not support the vectorcall protocol (either because the type does not or because the specific instance does not), return NULL . Otherwise, return the vectorcall function pointer stored in op . This function never raises an exception.
This is mostly useful to check whether or not op supports vectorcall, which can be done by checking PyVectorcall_Function(op) != NULL .
PyVectorcall_Function(op) != NULL
调用 callable ’s vectorcallfunc with positional and keyword arguments given in a tuple and dict, respectively.
vectorcallfunc
This is a specialized function, intended to be put in the tp_call slot or be used in an implementation of tp_call . It does not check the Py_TPFLAGS_HAVE_VECTORCALL flag and it does not fall back to tp_call .
Various functions are available for calling a Python object. Each converts its arguments to a convention supported by the called object – either tp_call or vectorcall. In order to do as little conversion as possible, pick one that best fits the format of data you have available.
The following table summarizes the available functions; please see individual documentation for details.
函数
callable
args
kwargs
PyObject *
dict/ NULL
NULL
PyObject_CallNoArgs()
PyObject_CallOneArg()
PyObject_CallObject()
tuple/ NULL
PyObject_CallFunction()
PyObject_CallMethod()
obj + char*
char*
PyObject_CallFunctionObjArgs()
PyObject_CallMethodObjArgs()
PyObject_CallMethodNoArgs()
PyObject_CallMethodOneArg()
PyObject_VectorcallDict()
Call a callable Python object callable , with arguments given by the tuple args , and named arguments given by the dictionary kwargs .
args 不得为 NULL ; use an empty tuple if no arguments are needed. If no named arguments are needed, kwargs 可以是 NULL .
Return the result of the call on success, or raise an exception and return NULL 当故障时。
This is the equivalent of the Python expression: callable(*args, **kwargs) .
Call a callable Python object callable without any arguments. It is the most efficient way to call a callable Python object without any argument.
Call a callable Python object callable with exactly 1 positional argument arg and no keyword arguments.
Call a callable Python object callable , with arguments given by the tuple args . If no arguments are needed, then args 可以是 NULL .
This is the equivalent of the Python expression: callable(*args) .
callable(*args)
Call a callable Python object callable , with a variable number of C arguments. The C arguments are described using a Py_BuildValue() style format string. The format can be NULL , indicating that no arguments are provided.
Py_BuildValue()
Note that if you only pass PyObject * args, PyObject_CallFunctionObjArgs() is a faster alternative.
3.4 版改变： 类型对于 format was changed from char * .
char *
Call the method named name of object obj with a variable number of C arguments. The C arguments are described by a Py_BuildValue() format string that should produce a tuple.
The format can be NULL , indicating that no arguments are provided.
This is the equivalent of the Python expression: obj.name(arg1, arg2, ...) .
obj.name(arg1, arg2, ...)
Note that if you only pass PyObject * args, PyObject_CallMethodObjArgs() is a faster alternative.
3.4 版改变： The types of name and format were changed from char * .
Call a callable Python object callable , with a variable number of PyObject * arguments. The arguments are provided as a variable number of parameters followed by NULL .
This is the equivalent of the Python expression: callable(arg1, arg2, ...) .
callable(arg1, arg2, ...)
Call a method of the Python object obj , where the name of the method is given as a Python string object in name . It is called with a variable number of PyObject * arguments. The arguments are provided as a variable number of parameters followed by NULL .
Call a method of the Python object obj without arguments, where the name of the method is given as a Python string object in name .
Call a method of the Python object obj with a single positional argument arg , where the name of the method is given as a Python string object in name .
Call a callable Python object callable . The arguments are the same as for vectorcallfunc 。若 callable supports vectorcall , this directly calls the vectorcall function stored in callable .
调用 callable with positional arguments passed exactly as in the vectorcall protocol, but with keyword arguments passed as a dictionary kwdict 。 args array contains only the positional arguments.
Regardless of which protocol is used internally, a conversion of arguments needs to be done. Therefore, this function should only be used if the caller already has a dictionary ready to use for the keyword arguments, but not a tuple for the positional arguments.
Call a method using the vectorcall calling convention. The name of the method is given as a Python string name . The object whose method is called is args[0] ，和 args array starting at args[1] represents the arguments of the call. There must be at least one positional argument. nargsf is the number of positional arguments including args[0] , plus PY_VECTORCALL_ARGUMENTS_OFFSET 若值 args[0] may temporarily be changed. Keyword arguments can be passed just like in PyObject_Vectorcall() .
If the object has the Py_TPFLAGS_METHOD_DESCRIPTOR feature, this will call the unbound method object with the full args vector as arguments.
Py_TPFLAGS_METHOD_DESCRIPTOR
Determine if the object o is callable. Return 1 if the object is callable and 0 otherwise. This function always succeeds.
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