python如何查看內(nèi)置函數(shù)源碼

如題，如何查看python內(nèi)置函數(shù)的源碼

舉個(gè)例子：

# 該以什么樣的方式，才能去看xrang的官方源碼實(shí)現(xiàn)
for i in xrange(10):
  print i

# 直接點(diǎn)進(jìn)去的話，大多都是一些定義的方法名，而沒(méi)有具體實(shí)現(xiàn)
# 就是想知道，如何去看具體實(shí)現(xiàn)，而不是下面那一堆 pass
class xrange(object):
    """
    xrange(stop) -> xrange object
    xrange(start, stop[, step]) -> xrange object
    
    Like range(), but instead of returning a list, returns an object that
    generates the numbers in the range on demand.  For looping, this is 
    slightly faster than range() and more memory efficient.
    """
    def __getattribute__(self, name): # real signature unknown; restored from __doc__
        """ x.__getattribute__('name') <==> x.name """
        pass

    def __getitem__(self, y): # real signature unknown; restored from __doc__
        """ x.__getitem__(y) <==> x[y] """
        pass

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

    def __iter__(self): # real signature unknown; restored from __doc__
        """ x.__iter__() <==> iter(x) """
        pass

    def __len__(self): # real signature unknown; restored from __doc__
        """ x.__len__() <==> len(x) """
        pass

    @staticmethod # known case of __new__
    def __new__(S, *more): # real signature unknown; restored from __doc__
        """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
        pass

    def __reduce__(self, *args, **kwargs): # real signature unknown
        pass

    def __repr__(self): # real signature unknown; restored from __doc__
        """ x.__repr__() <==> repr(x) """
        pass

    def __reversed__(self, *args, **kwargs): # real signature unknown
        """ Returns a reverse iterator. """
        pass