19-08-2009 o 00:47:09 David <davidsh...@googlemail.com> wrote:
Hi all,
I'm trying to understand how scopes work within a class definition.
I'll quickly illustrate with an example. Say I had the following class
definition:
class Abc:
message = 'Hello World'
def print_message(self):
print message
instance = Abc()
instance.print_message()
NameError: global name 'message' not defined
My question is, why? message is not defined in print_message, but it
is defined in the enclosing scope (the class)?
Note that when *running* the code that is *inside* print_message() method
called within the global scope, the outer (enclosing) scope is indeed the
global scope (the scope in which e.g. 'instance' name exists; note that
e.g. 'print instance' in that method would be ok).
As Chris wrote, class' scope (contrary to outer function scope) is not
considered as the 'enclosing' scope.
The only ways to reach Abc's attribute 'message' from that method are:
* 'Abc.message'
* 'self.__class__.message'
* 'self.message' (unless there is an instance attribute 'message' which
overrides the class attribute).
Cheers,
*j
--
Jan Kaliszewski (zuo) <z...@chopin.edu.pl>
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