question on global variables

[Mark McEahern]

> Somewhat new to Python here.....
>
> I want to change/use a value throughout my program - what I would normally
> refer to as a "global" variable.
>
> I see that there is a "global" command - and I assume its use would be
> global var_name. This I have coded (works) but I am unable to use
> it "global name var_name is not defined".

Consider the following example.  It should make you retch:

***

#!/usr/bin/env python

global i
i = 1

def foo():
    global i
    i += 1

def bar():
    global i
    i += 1

foo()
bar()

print i

***

Why should it make you retch?  Because there's no reason whatsoever for me
to use global--foo and bar would be much clearer if they operated on input
and returned as output whatever they need to communicate to their callers:

***

#!/usr/bin/env python

def foo(i):
    return i + 1

def bar(i):
    return i + 1

i = 1
i = foo(i)
i = bar(i)

print i

***

In other words--why let the fact that Python has a global statement fool you
into thinking you've found a problem for which it's the only much less the
best hammer?

Cheers,

// mark

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