New submission from Maxime Lemonnier <[email protected]>:
Consider the following code sample :
keys = ['x', 'y', 'z']
d = dict.fromkeys(keys, [])
d['x'].append('dont')
d['y'].append('mix')
d['z'].append('me!')
print d['x']
>>> ['dont', 'mix', 'me!']
It is very unatural and dangerous to have all dict keys poining to the
same mutable object reference.
The way it should behave :
if value is mutable, create a new copy of value for each keys
else, it doesn't matter
----------
components: Interpreter Core
messages: 91714
nosy: maxlem
severity: normal
status: open
title: dict.fromkeys() should not cross reference mutable value by default
type: behavior
versions: Python 2.6
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Python tracker <[email protected]>
<http://bugs.python.org/issue6730>
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