[Python-bugs-list] [ python-Bugs-476616 ] UserDict.copy() error (original) (raw)

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Tue, 30 Oct 2001 19:32:54 -0800

Bugs item #476616, was opened at 2001-10-30 18:57 You can respond by visiting: http://sourceforge.net/tracker/?func=detail&atid=105470&aid=476616&group_id=5470

Category: Python Library Group: Python 2.2 Status: Open Resolution: None Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: UserDict.copy() error

Initial Comment: The copy() method applied to subclasses of UserDict copies the object, but does not copy the contained dictionary. The dictionary is shared between the original and the copy.

The copy method applied to UserDict (not a subclass) works okay.

This error goes back to at least 2.0, and still exists in 2.2b1.

This little test program demonstrates the error:

from UserDict import UserDict

class MyDict (UserDict): pass

d = MyDict() d[1] = 11 c = d.copy() c[2] = 22 # this should affect c only, but also affects d print "c:", c print "d:", d

BTW, subclassing 'dictionary' works fine in 2.2 (of course). For running under 2.0, I worked around this by using copy.deepcopy().

I'm in no hurry for a fix for this.

Bob Alexander balexander@rsv.ricoh.com

Comment By: Guido van Rossum (gvanrossum) Date: 2001-10-30 19:32

Message: Logged In: YES user_id=6380

Hm, you're right. Sigh. This has been there since 1.5.2. I'm not sure how to fix this -- using deepcopy() is too much (and not what happens if self.class is UserDict either). Maybe this: c = copy.copy(self) c.data = self.data.copy() return c

You can respond by visiting: http://sourceforge.net/tracker/?func=detail&atid=105470&aid=476616&group_id=5470