[Python-bugs-list] [ python-Bugs-592573 ] UserString is mutable via +=

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Bugs item #592573, was opened at 2002-08-08 08:48
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Category: Python Library
>Group: Python 2.3
Status: Open
>Resolution: Accepted
Priority: 5
Submitted By: Bernhard Herzog (bernhard)
>Assigned to: Raymond Hettinger (rhettinger)
Summary: UserString is mutable via +=

Initial Comment:
UserString is mutable with augmented assignment:

Python 2.2 (#1, Jan 17 2002, 21:04:07) 
[GCC 2.95.4 20011006 (Debian prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for
more information.
>>> import UserString
>>> s = t = UserString.UserString("abc")
>>> s += "def"
>>> s
'abcdef'
>>> t
'abcdef'
>>> 


The __iadd__ and __imul__ methods should be in the
MutableString class I think.

OTOH, nowadays the string types can be sub-classed so
that UserString behaving exactly like a builtin string
may not be that important anymore.


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>Comment By: Guido van Rossum (gvanrossum)
Date: 2002-08-08 21:22

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Hm, I think this is indeed a bug. I've never used UserString
myself nor reviewed the code. I think your patch is okay, so
go ahead in 2.3.

This will create a backwards incompatibility; I'm not sure
it's a good idea to "fix" it in 2.2.2.

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Comment By: Raymond Hettinger (rhettinger)
Date: 2002-08-08 21:09

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Patch and unittest attached for review.
Possible 2.2 release-maint candidate.

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Comment By: Raymond Hettinger (rhettinger)
Date: 2002-08-08 13:51

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Thanks for the bug report.

Will patch to bring behavior back in-line with string 
methods as promised by the docs.

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