On Sun, Jun 26, 2011 at 11:28 AM, Marc Aymerich <glicer...@gmail.com> wrote: > Hi, > I'm trying to define a function that has an optional parameter which > should be an empty list whenever it isn't given. However, it takes as > value the same value as the last time the function was executed. What > is the reason of this behaviour? How does python deal with default > values (i.e. when are they assigned/created)? > > Thanks :) >
So the thing about Python is that you don't actually declare functions. You create them. def is an executable statement that creates a function object. Default arguments are part of the function object, so they get evaluated when the function is created. >>> foo Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'foo' is not defined >>> def foo(a = []) : ... a.append(1) ... >>> foo.func_defaults ([],) >>> foo() >>> foo.func_defaults ([1],) >>> -- http://mail.python.org/mailman/listinfo/python-list
