[Tutor] Why thus?
Sun, 12 Mar 2000 23:26:43 +0100
"Wesley J. Chun" wrote:
> > Date: Sun, 12 Mar 2000 22:29:57 +0100
> > From: Christian Tismer <email@example.com>
> > The difference is: When compiling your code, the compiler
> > tries to figure out what is global and what not. Since
> > counter is assigned to, it becomes a local. But the object
> > does not yet exist when you request it:
> > counter=counter+1
> > wants to retrieve the current value, and it isn't set yet.
> > You are accessing a local variable which already has its
> > slot and is ready to receive a value, but cannot until
> > it is initialized.
> chris is absolutely right. when doing an assignment in a
> local scope, the compiler will search only for the local
> name, and since you haven't done a "counter = XXX" within
> __init__(), it will complain.
Careful, in his exmple he wasn't referring to self
at all, and __init__() wouldn't have helped.
> # this fails (references local var that hasn't been
> # assigned/doesn't exist)
> i = 4
> def foo():
> print i # "print global 'i'"
> i = 6 # set local 'i'
> the result is a "NameError: i". upon seeing the presence
> of a local 'i' makes any previous code *think* it should
> access a local 'i' vs. the global one.
+++Please try to avoid false comments, this confuses
people who are not already sure what's right and what not.
Short conclusion: A name in a function is either local
or global. If it is assigned to, it is local, unless
spelled in a "global" statement. Non-assigned names
are always global.
> "Core Python Programming", Prentice-Hall, TBP Summer 2000
> (will have an example like this in here too!)
Also "Learning Python" can be recommended (not only because
I translated it into German :-)
ciao - chris
Christian Tismer :^) <mailto:firstname.lastname@example.org>
Applied Biometrics GmbH : Have a break! Take a ride on Python's
Kaunstr. 26 : *Starship* http://starship.python.net
14163 Berlin : PGP key -> http://wwwkeys.pgp.net
PGP Fingerprint E182 71C7 1A9D 66E9 9D15 D3CC D4D7 93E2 1FAE F6DF
we're tired of banana software - shipped green, ripens at home