[ python-Bugs-1467929 ] %-formatting and dicts

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Bugs item #1467929, was opened at 2006-04-10 19:39
Message generated for change (Comment added) made by gbrandl
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Category: Python Interpreter Core
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: M.-A. Lemburg (lemburg)
>Assigned to: Martin v. Löwis (loewis)
Summary: %-formatting and dicts

Initial Comment:
This looks like a bug in the way the %-formatting code
works or is it a feature ?

>>> '%s %(a)s' % {'a': 'xyz'}
"{'a': 'xyz'} xyz"

>>> u'%s %(a)s' % {'a': 'xyz'}
u"{'a': 'xyz'} xyz"

Note that both strings and Unicode are affected.

Python 2.3 and 2.4 also show this behavior.

I would have expected an exception or the %-formatter
simply ignoring the first %s.




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>Comment By: Georg Brandl (gbrandl)
Date: 2006-07-24 13:37

Message:
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The library ref specifies that if a dict is supplied, the
format specifiers MUST include a mapping key, so the right
thing to do would be to raise an exception.

Is it worth breaking backwards compatibility, Martin?

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Comment By: Hasan Diwan (hdiwan650)
Date: 2006-04-14 08:33

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It looks as though it's a feature... The first %s will print
the whole dictionary as a string, the second, only that
value looked up by the key.

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