使用多个函数参数调用PyObject_CallObject

Question

If I have a function in Python like this:

def multiply(a, b)
    return a * b

How can I call PyObject_CallObject when it will give me an error if I have more than two arguments? There may be a much better way of calling a function from C++ but I am very new to the Python/C API

Answer 1

From the documentation :

PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)

^{Return value: New reference.}

Call a callable Python object callable_object , with arguments given by the tuple args . If no arguments are needed, then args may be NULL . Returns the result of the call on success, or NULL on failure. This is the equivalent of the Python expression callable_object(*args) .

In other words:

• You can pass more than one argument to the function by passing a single tuple containing the arguments. So you'd have to build a tuple containing x and y (ie (x, y) ) and then pass the tuple as single parameter to PyObject_CallObject(multiply, the_tuple) this will be equivalent to multiply(x, y) .
• It does not represent the most general call. The most generic call is PyObject_Call which takes two arguments: a tuple of positional arguments and a dictionary of keyword arguments.
• There are also the PyObject_CallFunction* functions that are similar to PyObject_CallObject but they avoid having to create the tuple and allow multiple parameters.