什么是“正确"?将布尔值传递给Python C扩展的方法? [英] What is the "correct" way to pass a boolean to a Python C extension?

问题描述

这是python文档(http://docs.python.org/extending/extending.html)中的一个简单示例:

This is a simple example from the python documentation (http://docs.python.org/extending/extending.html):

static PyObject *
spam_system(PyObject *self, PyObject *args)
{
    const char *command;
    int sts;

    if (!PyArg_ParseTuple(args, "s", &command))
        return NULL;
    sts = system(command);
    return Py_BuildValue("i", sts);
}

如果我想向该函数传递一个附加的布尔参数-做到这一点的正确"方法是什么?

If I want to pass an additional boolean parameter to the function - what's the "correct" way to do it?

似乎没有传递给PyArg_ParseTuple()的布尔选项.所以我想到了以下几点:

There doesn't seem to be a bool option to pass to PyArg_ParseTuple(). So I thought of the following:

1. 读取一个整数并仅使用该值(因为bool是int的子类)
2. 以整数调用PyBool_FromLong()
3. 读取并反对，然后调用PyBool_Check()以确认它是布尔值
4. 也许有一种方法可以获取任何类型的变量并获取其真值(即，空数组将是虚假的，等等)，这是python函数通常执行的操作.

这些更可取吗?还有其他选择吗?

Any of these preferable? Other options?

推荐答案

4也许有一种方法可以获取任何类型的变量并获取其真值(即，空数组将是虚假的，等等)，这就是python 功能通常可以做到.

4 maybe there's a way to get any type of variable and get its truth value (i.e an empty array will is falsy etc.) which is what python function usually do.

是:(来自 Python/C API参考)

int PyObject_IsTrue(PyObject *o)

如果对象o被认为是真实的，则返回1，否则返回0. 这等效于Python表达式not o.失败了 返回-1.

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.

编辑.为了回答实际问题，我认为方法1是正确的，因为int确实是C中的对应类型.方法4很好，但是如果您将函数记录为bool，则您没有义务仅接受任何对象.在Python中，无缘无故地像3中那样进行显式类型检查.如2中那样转换为另一个Python对象对您的C代码没有帮助.

EDIT. To answer the actual question, I think approach 1 is correct, because int really is the corresponding type in C. Approach 4 is good, but if you document your function as taking a bool, you are not obligated to accept just any object. Explicit type checks as in 3 without a reason are frowned upon in Python. Conversion to another Python object as in 2 does not help your C code.

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