Well, your example still seems to be about accessing or modifying a global variable *within* its own module. Then it can't hurt to prepend 'global' even when just accessing, right? (even if not *necessary*, one could argue make the code clearer).
But, my question related specifically to another case: when another module import a second module and the importing module tries to access and modify the second module's "global" variable, which Kent's post explained is really a module attribute. Then, the dot notation seems needed. (Maybe its my use of 'global' in this context which causes misunderstanding?) 2007/4/15, Andreas Kostyrka <[EMAIL PROTECTED]>: > * Cecilia Alm <[EMAIL PROTECTED]> [070415 23:19]: > > 2007/4/15, Andreas Kostyrka <[EMAIL PROTECTED]>: > > >* Cecilia Alm <[EMAIL PROTECTED]> [070415 18:21]: > > >> If a module "x" imports module "y" with a global variable "z", then > > >> this global can be referred or assigned to in "x" with the syntax > > >> "y.z" (no "global" keyword preceding) and changes are accessible to > > >> class methods in "y" referring to "global z". > > > > > >Well, you don't need the global statement for accessing z. You need it > > >for modifying it, or Python will assume that you are working with a > > >local variable z. > > > > > > > Hm, I'm confused by your post. Within the global's module, the "global > > z" syntax works for bothh modifying and accessing, and makes the code > > clearer to read in my opinion. (Although, it may not be needed when > > accessing or when modifying mutable types.) > Well, the global is not needed for accessing the name. > > And the assume it's a local variable is meant serious: > > >>> def x(): > ... z += 1 > ... > >>> x() > Traceback (most recent call last): > File "<stdin>", line 1, in ? > File "<stdin>", line 2, in x > UnboundLocalError: local variable 'z' referenced before assignment > > It's one of the more baffling errors for newbies. > > The real reason is important to understand, it explains things like > self. and global: > > *) when accessing a name, it's easy to try out multiple namespaces > till you find the correct one. > *) when reassigning a name, it's way harder, because you cannot > automatically guess which namespace should be used. > > That's the reason why you need global statement, which makes > assignments to a name go to the module namespace. And that's one of > the reasons, why instance variables are accessed explicitly as self.name. > > Andreas > -- E. Cecilia Alm Graduate student, Dept. of Linguistics, UIUC Office: 2013 Beckman Institute _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
