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Thu Apr 5 11:47:11 EDT 2001 · http://mail.python.org/pipermail/python-list/2001-April/105930.html

Brian Elmegaard wrote:
> Can it be written in a few words, so I may understand why lists
> are (and have to be) so different from "normal" variables?

how about two and a half words: "they're not" ;-)

confusing?

let's go back to the "python objects" page.  the first set
of clues are hidden under "objects":

    "Some objects have methods that allow you to
    change the contents of the object."

(lists belong to this category.  you can use methods to
modify the contents of a list).

    "Some objects only have methods that allow you
    to access the contents, not change it."

("normal variables", like integers, floats, strings, belong to
this category.  if you want a new integer/float/string value,
you have to create a new object)

the second set of clues can be found under "assignments":

    "Assignment modify namespaces, not objects"

(when you type "s = 10", you're modifying a namespace, not
whatever "s" contained before.  anyone looking at the original
object won't see the change -- because nothing has changed!)

    "Things like name.attr and name[index] are just
    syntactic sugar for method calls."

(when you type "s[0] = 10", you ask whatever "s" points to
to replace item zero with a new value.  in your case, you ask
the list "s" to modify it's first item.  anyone else referring to
the same list object will see this change)

:::

now read alex' reply once or twice.  then read the "python
objects" page again, and make sure you understand every-
thing in there.  once you've done this, the standard docs
may start to make a little more sense ;-)

(or maybe you're more confused than ever.  in that case,
we do apologize for the inconvenience...)

Cheers /F

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Changing global variables in tkinter/pmw callback