surprising behaviour of os.environ.clear

Tim Roberts timr at
Sat Jun 28 08:23:18 CEST 2008

Benjamin <musiccomposition at> wrote:
>On Jun 27, 4:05 pm, "Joe P. Cool" <joe.p.c... at> wrote:
>> If I call os.environ.clear in a python program child processes still
>> see the deleted entries. But when I iterate over the keys like so
>> names =  os.environ.keys
>> for k in names:
>>     del  os.environ[k]
>> then the entries are also deleted for the child processes. Where is
>> the difference? Is this a bug?
>> (Observed in Python 2.5.2)
>This is because of how os.environ is implement with a UserDict

Why?  I mean, I can see that it happens, but I don't understand why being a
UserDict causes this.
Tim Roberts, timr at
Providenza & Boekelheide, Inc.

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