[New-bugs-announce] [issue4181] Invalid Behavior When a Default Argument is a Dictionary.

Pasha report at bugs.python.org
Wed Oct 22 23:52:18 CEST 2008

New submission from Pasha <pavel.kamyshev at yale.edu>:

Whenever the default argument to a function is a dictionary, and the
function is called twice, then the function "remembers" the changes to
the dictionary. 

This means that any time that a default argument is set to a dictionary,
a list or any other built in data structure, it cannot be relied upon to
correctly do the right thing. 

I assume this is actually two issues:

1) The default arguments are not being garbage collected after the
function is done. You can check that by using a __del__ tracker 

2) the argument is at the same memory location at all times. 

I have seen this on Python 2.5.2, however its highly possible other
parts are affected as well.

components: Interpreter Core
files: default_argument_dictionary_bug.py
messages: 75114
nosy: Pasha2009
severity: normal
status: open
title: Invalid Behavior When a Default Argument is a Dictionary.
type: behavior
versions: Python 2.5
Added file: http://bugs.python.org/file11861/default_argument_dictionary_bug.py

Python tracker <report at bugs.python.org>

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