为什么__repr__ function在定义class时可以自己使用repr()？（Python）

Question

class Link:

    def __init__(self, first, rest=empty):
        assert rest is Link.empty or isinstance(rest, Link)
        self.first = first
        self.rest = rest

    def __repr__(self):
        if self.rest is not Link.empty:
            rest_repr = ', ' + repr(self.rest)
        else:
            rest_repr = ''
        return 'Link(' + repr(self.first) + rest_repr + ')'

    def __str__(self):
        string = '<'
        while self.rest is not Link.empty:
            string += str(self.first) + ' '
            self = self.rest
        return string + str(self.first) + '>'

This is defining code of Link(ielinked list).And the __repr __function's output is like

>>> s = Link(5,Link(6))
>>> s                                   # Displays the contents of repr(s)
Link(5, Link(6))

But I cann't understand why the __repr__ function can use repr(self.first) in itself.I think that would cause inifinite loop.

I wonder:Is the repr function a built-in funciton in Python even though I am defining the __repr__ function?(Just like the str can be used in the __str__ function?)

Answer 1

    def __repr__(self):
        if self.rest is not Link.empty:
            rest_repr = ', ' + repr(self.rest)

Look at this piece of code, what do you notice?

Exactly: you are using repr(self.rest) , which is equivalent to self.rest.__repr__() .

In other words you aren't calling repr on an instance of Link , but just on an attribute of it. So you aren't calling Link.__repr__ into its body, don't worry.