python中chain的源代码在哪里？ [复制]

Question

我想在 python itertools 中查看链的源代码，但这是我在源代码中找到的？为什么他们都是'通过'？

class chain(object):
    """
    chain(*iterables) --> chain object

    Return a chain object whose .__next__() method returns elements from the
    first iterable until it is exhausted, then elements from the next
    iterable, until all of the iterables are exhausted.
    """
    @classmethod
    def from_iterable(cls, iterable): # real signature unknown; restored from __doc__
        """
        chain.from_iterable(iterable) --> chain object

        Alternate chain() contructor taking a single iterable argument
        that evaluates lazily.
        """
        pass

    def __getattribute__(self, *args, **kwargs): # real signature unknown
        """ Return getattr(self, name). """
        pass

    def __init__(self, *iterables): # real signature unknown; restored from __doc__
        pass

    def __iter__(self, *args, **kwargs): # real signature unknown
        """ Implement iter(self). """
        pass

    @staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

Answer 1

您看到的类可能是另一个模块。 Itertools 和许多其他内置函数是用编译后的 c 编写的。你可以在这里阅读 cpython 代码 https://github.com/python/cpython/blob/3.6/Modules/itertoolsmodule.c#L1792

在 itertools 文档中，它指出链函数大致相当于：

 def chain(*iterables):
    # chain('ABC', 'DEF') --> A B C D E F
    for it in iterables:
        for element in it:
            yield element