[Tutor] __repr__ and __str__

[Steven D'Aprano]

On Mon, Jun 29, 2015 at 11:47:45PM -0700, Marilyn Davis wrote:
> Hello Python Tutors,
> 
> A student has asked a question that has me stumped.  We are using 2.7.

Ooh, nice one! That had me stumped for a while too, but I think I have 
the solution. I wrote this class to investigate:

class MyList(list):
    def __str__(self):
        print "called __str__"
        return list.__str__(self)
    def __repr__(self):
        print "called __repr__"
        return list.__repr__(self)



Then I ran this in the interactive interpreter:

py> L = MyList([1, 2, 3])
py> repr(L)
called __repr__
'[1, 2, 3]'
py> str(L)
called __str__
called __repr__
'[1, 2, 3]'


So what appears to be happening is that list.__str__ calls __repr__. My 
guess is that it is written something like this:

# built-in list
class list:
    def __str__(self):
        return self.__repr__()



-- 
Steve