problem with variable scoping

[Hans Nowak]

On 26 May 99, Michael Dingler wrote:

> It's...
> 
> an embarassing question. Yes folks, I'm writing my first
> Python program (a text to HTML converter) and I have a
> slight misunderstanding with the variable scoping...
> 
> Let me present some code fragments:
> 
> last_line_empty = 0
> .
> .
> .
> def process(line):
> 	...
> 	if last_line_empty:
> 		pass
> 	else:
> 		print "<P>"
> 	last_line_empty = 1

Add this line

	global last_line_empty

as the first line in your process function. Python's scoping is 
different from, say, C's. Let's say I have this code:

x = 1

def p():
	x = 2

then the x in function p is considered *local*. A similar construct 
in C or Pascal would access the global variable x; not so in Python. 
If you want to change this behavior, you can use the global 
specifier. So this:

def q():
	global x
	x = 2

*would* access global variable x.

I'll be darned if this isn't in the FAQ somewhere. :o)  [looks it up] 
Try questions 4.36 and 4.57. They pretty much deal with this problem. 
It used to bite me too when I started with Python.

Veel liefs,


--Hans Nowak (ivnowa at hvision.nl)
Homepage: http://fly.to/zephyrfalcon