[Tutor] advice on global variables

[Chris Hare]

I know they are bad.  That is why I would prefer not to use it, but I am not sure how else to handle this problem.

In this app, the user must log in.  Once authenticated, they have a userid stored in the SQLite database.  Before splitting my app into multiple files, I used a global variable.  I know its bad, but it worked.  Now that things are split apart, the classes which used it previously now don't see it anymore, even using the global keyword.  I think this is the expected behavior.  See here

file: a.py

import b
global_var = "global"

def func1():
	global global_var
	print "global var in func1 = %s" % global_var

class intclass:
	def func2(self):
		global global_var
		print "global var in intclass = %s" % global_var

print "global_var = %s" % global_var
func1()
f = intclass()
f.func2()
g = b.extclass()
g.func3()

file: b.py

class extclass:
	def func3(self):
		global global_var
		print "global var in extclass = %s" % global_var

When I run it, I get what I think the expected behavior, that the external class ext class won't be able to see the global_var

Big-Mac:t chare$ python a.py
global_var = global
global var in func1 = global
global var in intclass = global
Traceback (most recent call last):
  File "a.py", line 18, in <module>
    g.func3()
  File "/Users/chare/Development/python/animaltrax/pkg/t/b.py", line 5, in func3
    print "global var in extclass = %s" % global_var
NameError: global name 'global_var' is not defined

So - my question is this:  how do I solve the problem of multiple classes needing to get access to a value which needs to be preserved across the lifetime of the running application?

One thought was a RAM based SQLite database, but that seems like a lot of work.  I dunno, maybe that is the option.

suggestions, ideas, criticisms are all welcome.  Python code aside, I just don't know how to approach this problem in Python.

Thanks, as always for the feedback and guidance.