name error

[Gordon McMillan]

Benjamin Derstine writes:

> test=line[0]
> location=line[0]
> 
> def makeuser():
>      mastlist=[]
>      while test==location:
>           list=f.readline()
>           location=list[0]
>           mastlist.append(list)
> makeuser()
> 
> error:
> 
> File "C:\WINNT\Profiles\bend\Desktop\licensing\loadtest.py", line
> 16, in makeuser
>     while test==location:
> NameError: location
> 
> It seems like I'm having a name space problem but there is nothing
> different between the test and the location variables when it comes
> to namespace. 

Oh yes there is. Just not at all what you expect.

> Yet one works and the other doesn't.  Anything I'm
> doing wrong?

makeuser assigns to location. In the absence of a "global" statement, 
Python makes the assumption that location is a local (to makeuser). 
So when it first hits " while test==location: ", it looks at the 
(local) location, which has not been initialized. A "global location" 
right after the def will tell Python to use the global var.

This is gotcha #3 - right after 1 / 2 == 0 and what happens when you 
use a mutable object as a default.

- Gordon