...
> =A0module Foo
>
> =A0 =A0CONSTANT_1 =3D 'bla'
> =A0 =A0CONSTANT_2 =3D foo('bla')
>
> =A0 =A0def self.foo(i) # i is a string that will be shortened.

As Robert described, the call to foo in assignment to CONSTANT_2
occurs before foo is defined

cheers