On 10/12/13 2:20 AM, Ian Kelly wrote:
On Fri, Oct 11, 2013 at 7:31 AM, Stephen Tucker <stephen_tuc...@sil.org> wrote:
On the original question, well, I accept Ned's answer (at 10.22). I also
like the idea of a helper function given by Peter Otten at 09.51. It still
seems like a crutch to help poor old Python 2.X to do what any programmer
(or, at least the programmers like me :-) ) think it ought to be able to by
itself. The distinction between the "geekiness" of a tuple compared with the
"non-geekiness" of a string is, itself, far too geeky for my liking. The
distinction seems to be an utterly spurious - even artificial or arbitrary
one to me. (Sorry about the rant.)
I agree, and that's not how I would explain the distinction. The str
of an object is meant to be human-readable, while the repr of an
object is meant to be something that could be pasted into the
interpreter to reconstruct the object. In the case of tuples, the
repr of the tuple uses the reprs of the components because the
resulting string will more likely be acceptable to the interpreter,
and the str of the tuple is the same as the repr because there is no
convincing reason why it should be different.
This idea that the repr can reconstruct the object always fell flat with
me since the vast majority of classes don't have a repr that works that
way. I look at it a little differently: the repr is meant to be as
unambiguous as possible to a developer. It turns out that Python
literal syntax is really good at that, so where possible, that's what's
used. But most classes don't make an attempt to create a Python
expression, because that's very difficult, and in fact, the literal
syntax may not be useful:
>>> object()
<object object at 0x1088bb0d0>
Here, the valid Python syntax is "object()", but that's useless as a
repr, because it doesn't help you distinguish between two instances.
In fact, you say repr could be used to "reconstruct the object", but
really what you mean is "reconstruct an equal object". There is no way
to construct an equal object(), so right at the root of the Python
object hierarchy, repr doesn't even attempt it.
--Ned.
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