使用PyArg_ParseTuple解析用户定义的类型 [英] Parsing User Defined Types Using PyArg_ParseTuple

问题描述

如何使用PyArg_ParseTuple解析用户定义的类型(或现有非标准库中的类型)?

How to parse userdefined types (or types from an existing non-standard library) using PyArg_ParseTuple?

推荐答案

我通常不喜欢使用

Instead of using the plain O format, as Martijn suggested, I normally prefer using the O& format. It allows you to pass a function that will be called to convert any PyObject* to an arbitrary C (double) pointer. Here is some example usage, in which I'm converting a passed value to a pointer to my own object type:

/** 
 * This method should return 0 if it does not work or 1 in case it does
 * PyArg_*() functions will handle the rest from there or let your program
 * continue in case things are fine.
 */
int MyConverter(PyObject* o, MyOwnType** mine) {
  //write the converter here.
}

然后，在此时需要解析对象:

Then, at the point you need to parse your object:

/**
 * Simple example
 */
static PyObject* py_do_something(PyObject*, PyObject* args, PyObject* kwds) {

    /* Parses input arguments in a single shot */
    static char* kwlist[] = {"o", 0};

    MyOwnType* obj = 0; ///< if things go OK, obj will be there after the next call

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&", kwlist, &MyConverter, &obj))
      return 0; ///< we have failed, let Python check exceptions.

    /* if you get to this point, your converter worked, just use */
    /* your newly allocated object and free it, when done. */

}

这种方法的优点是您可以将MyConverter封装在C-API上，然后在同一功能的其他功能中重新使用它.

The advantage of this approach is that you can encapsulate your MyConverter on a C-API and then re-use it in other functions for the the same job.

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