[Python-ideas] about repr

[Georg Brandl]

spir schrieb:
> Hello,
> 
> -1- repr writing function
> 
> Wonder if you would like a statement (py2) or function (py3) similar to print, except that it would output the repr form instead of str. I would enjoy having such a nicety to avoid "print repr(x)" or "print(repr(x))".
> 
> As a side note, there is imo something missing in the // below:
>    __str__    str()    %s   print
>    __repr__   repr()   %r   (show?)
> If only for consistency... it wouldn't hurt.

Use ``from sys import displayhook as show`` ;)

> -2- use for test purpose 
> 
> I just read the following by Ka-Ping Yee on python-dev (http://mail.python.org/pipermail/python-dev/2000-April/003238.html):
> """
> repr() is for the human, not for the machine.  [Serialization]
> is for the machine.  repr() is: "Please show me as much information
> as you reasonably can about this object in an accurate and unambiguous
> way, but if you can't readably show me everything, make it obvious
> that you're not."
> """
> 
> I see str() as intended to produce a view of an object that has a kind of "natural" (read: cultural) textual form, like a date, and rather for the user. repr() instead seems to me more "rough", informative, and programmer-oriented. 
> For this reason, I heavily use repr for test, usually have a __repr__ method on custom classes only for that purpose.
> 
> I would like to know how much debug work is done without help of a debugger. I suspect it's a rather high percentage for several reasons, especially with a clear and friendly language like python. At test/debug/setup time it's often enough to have some variable output at the proper time & place. But we often need several values at several points. 
> The one thing missing is then the names of the variables showed. So that we have to insert eg
> 	print "x:%r" % x

Use ``from pprint import pprint; pprint(vars())``.

Georg

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