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From: Chris Angelico <rosuav@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: What is a function parameter =[] for?
Date: Thu, 19 Nov 2015 22:58:33 +1100
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On Thu, Nov 19, 2015 at 10:41 PM, BartC <bc@freeuk.com> wrote:
> As I said, it's bizarre. It means that for certain types, Python doesn't
> have a default that works per call, but only a default that works once per
> program.

No, it's not "for certain types". Regardless of the type, the
expression that defines the default is evaluated at *function
definition*, not at each *function call*. (That's not the same as
"once per program", although for 99% of situations, it'll be
indistinguishable.)

ChrisA