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annotate python/mutable_defaults.py @ 333:998d3c276b25

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http://askubuntu.com/questions/168117/how-to-automatically-add-meta-tags-to-screenshot?rq=1
author Jeff Hammel <jhammel@mozilla.com>
date Tue, 18 Jun 2013 14:44:14 -0700
parents 434c65593612
children
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70544c7406e2 add illustration program for mutable arguments, since this comes up a bunch
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1 #!/usr/bin/env python
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2
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3 # see also: http://www.daniweb.com/software-development/python/threads/66697
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4
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5 class Foo(object):
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6 def __init__(self, mutable=['default']):
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7 self.foo = mutable
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8 self.foo.append(1)
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9
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10 if __name__ == '__main__':
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11 bar = Foo()
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12 print len(bar.foo)
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13 fleem = Foo()
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14 print len(fleem.foo)
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15 assert len(fleem.foo) == 2, "Don't use default mutable arguments!"