[Tutor] Confused about globals

[Kent Johnson]

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 = {}
	in_file=open("well_xy.txt","r")
	for line in in_file
		L=line.split()
		well=L[0]
		x=L[1]
		y=L[2]

		D[well]=(x, y)
	in_file.close()
	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 
operations.

Kent