[Python-3000] PEP 3138- String representation in Python 3000

[Jim Jewett]

On 5/26/08, Adam Olsen <rhamph at gmail.com> wrote:
> On Mon, May 26, 2008 at 5:24 PM, Oleg Broytmann <phd at phd.pp.ru> wrote:

>  >   There are two different and unrelated problems. One is that
>  > str(container) calls repr() on items. This probably could be fixed with
>  > a flag to repr() so it remembers it was called from str(). This has nothing
>  > with hex-encoding strings - calling str() on items would be a win in any
>  > case, especially for items that implements both __str__ and __repr__
>  > methods.

> There's a reason for that convention.  Would you prefer str(['1', '2',
>  '3']) return '[1, 2, 3]'?

I don't think anyone is arguing about how to display

    >>> "%" % string

The problem is classes where str(x) != repr(x), and how they get
messed up when a container holding (one of their) instances is
printed.

>>> class A:
	def __str__(self):  return "an A"
>>> a=A()

>>> print a    # this is fine.
an A
>>> str(a)      # this is OK, you have asked for "%s" % a
'an A'
>>> repr(a)   # this is OK, you wanted repr explicitly.
'<__main__.A instance at 0x012DDAF8>'

>>> print ([a])   # this stinks ...
[<__main__.A instance at 0x012DDAF8>]

It would be much better as:

>>> print ([a])   # after fixing the recursion bug
['an a']



Whereas you are asking about the (perhaps also acceptable):

>>> # after fixing the recursion bug,
>>> print ([a])   # and somehow not even applying str
[an a]

-jJ