Newbie question

[Paul Osman]

Ante,

do some reading about scope... add the following line to dummy.py:

<code>
num = 0

def dummy():
    global num
    num += 1

dummy()
</code>

now in the interpretor:
 >>> import dummy
 >>> print dummy.num
1
 >>> dummy.dummy()
 >>> print dummy.num
2

HTH,

-Paul Osman

Ante wrote:

>from file 'dummy.py'
>----------------------------
>num = 0
>
>def dummy():
>    num += 1
>
>dummy()
>----------------------------
>
>now, in the interpreter:
>
>>>>import dummy
>>>>
>Traceback (most recent call last):
>  File "<string>", line 1, in ?
>  File "C:\downloads\python2.2.1\dummy.py", line 6, in ?
>    dummy()
>  File "C:\downloads\python2.2.1\dummy.py", line 4, in dummy
>    num += 1
>UnboundLocalError: local variable 'num' referenced before assignment
>
>
>Why does this happen?
>If I replace num += 1 with print num, it prints 0 without an error.
>I guess it scans the whole function and check if there's an assignment to a
>name,
>and if there is, assumes it's a local variable. But += isn't supposed to
>move the
>reference but instead change the same variable. Or what did I get wrong?
>
>Ante.
>
>
>