How to initialize a class variable once

John Machin sjmachin at
Tue Dec 9 05:44:53 CET 2008

On Dec 9, 3:36 pm, Matimus <mccre... at> wrote:
> On Dec 8, 8:08 pm, Roy Smith <r... at> wrote:
> > I've got a class with a class variable:
> > class Foo:
> >    _map = {}
> > How do I make sure this only gets initialized the *first* time the
> > module containing the class is imported?  What appears to be happening
> > as it stands is each time the module gets imported, Foo._map get re-
> > initialized.
> Unless you are calling reload() on the module, it will only ever get
> _loaded_ once. Each additional import will just yield the existing
> module. Perhaps if you post an example of the behavior that leads you
> to believe that the class variables are getting reinitialized

and change it to
   class Foo(object):
because we care little about old-style classes these days
and put a print statement in the module just before the class
statement and print statements before and after each import statement
so that we can see what is happening.

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