[Tutor] Confused about globals

Kent Johnson kent37 at tds.net
Fri Jun 9 16:44:42 CEST 2006

Etrade Griffiths wrote:
> Hi
> I have a series of python programs that plot stuff using PYX.  Common to 
> these is the need to read in a list of (well) locations in (X,Y) coords so 
> I put that code in a separate module called shared_funcs.py.  The coords 
> are stored in dictionaries which I want to use later in the "main" program 
> - every time I find a well with data, I can get the well's (x,y) coords by 
> looking up the well name in the dictionary.  

You don't need a global variable in shared_funcs.get_xy_data() at all. 
It is reading a file and creating two dicts. I would write it to create 
and return the dicts. Then you can save them where you like in the 
caller. Also, I would use one dict whose values are (x, y) pairs, rather 
than two parallel dicts. Then your code looks like this:

=== shared_funcs.py ===

def get_xy_data():
	D = {}
	for line in in_file

		D[well]=(x, y)
	return D

=== main.py ===

import shared_funcs
D = shared_funcs.get_xy_data()

though I suggest a more descriptive name than D...

If there are other related bits of data or operations other than lookup, 
that might point to using a class to wrap the dict, the other data and 


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