At 01:05 AM 6/28/2008, Alan Gauld wrote:
"Dick Moores" <[EMAIL PROTECTED]> wrote
I'm puzzled by the below error msg. If I change the line in a2() from
l1 = [1,2,3]*100
This is not in a2() this is in the global namespace outside of a2.
a2() consists of a single assignment statement. And assignment
inside a function creates a local variable which in this case
masks the global variable. But the local variable assignment
uses the same variable which is not allowed so you get the
error message.
Why? And why isn't that line a problem for a1()?
In a1 you don't assign so you never create a local variable
you use the global variable
=========================================
def a1():
return l1.extend(l2)
No assignment, it returns the global value
if __name__=='__main__':
l1 = [1,2,3]*100
t = Timer("a1()", "from __main__ import a1")
def a2():
l1 += l2
new local variable "created" but erroneously. Change to
def a2():
global I1
I1 += I2
return I1
See my tutor topic on namespaces for more on this theme.
Thanks very much Alan. I think I've got it now, but I will study that
section in your tutorial.
And my thanks also to Douglas Drumond.
>>> import this
[snip]
Namespaces are one honking great idea -- let's do more of those!
>>>
Dick
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