[EMAIL PROTECTED] wrote: > Hi, > > Can anyone explain the following: > > Python 2.5 (r25:51908, Apr 9 2007, 11:27:23) > [GCC 4.1.1 20060525 (Red Hat 4.1.1-1)] on linux2 > Type "help", "copyright", "credits" or "license" for more information. > >>>>def foo(): > > ... x = 2 > ... > >>>>foo() >>>>def bar(): > > ... x[2] = 2 > ... > >>>>bar() > > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > File "<stdin>", line 2, in bar > NameError: global name 'x' is not defined > > Thanks, > Jianbing >
1. Each function call creates its own namespace, so "x" in foo() is "isolated" from the global namespace or from calls of bar(). 2. Think of assignment as assigning a name to a value rather than "putting a value" into the name. When you assign, you completely change the identity of name, rather than changing the contents of the name. For example: py> x = object() py> id(x) 1074201696 py> x = object() py> id(x) 1074201704 Notice how the identity (id) of x changes. James -- http://mail.python.org/mailman/listinfo/python-list
