python中真正的全局变量

Question

OK so the project I am working on requires* using a truly global variable (or five) and the other questions on here have to do with cross module variables (could be helpful later just not yet).

Here is my problem: I have a program that will be running an environmental simulation and I need to set some global variables to be used and modified inside some of the functions. How would one go about doing that?

*When I say require I mean that I haven't found a more efficient way to do this.

Answer 1

Yes, there is a way to use and modify global variables inside functions that are spread across several modules. Put the variables in a module and import that module into your main program:

# globals.py
klaatu = "Once in Persia reigned a king ..."

# main_program.py
import globals

def modify_klaatu():
    print globals.klaatu
    globals.klaatu = "It was the best of times, it was the worst of times."

Answer 2

A somewhat dodgy but entirely dynamic variant of @rob's approach:

import types
import sys

sys.modules['myglobals'] = types.ModuleType('myglobals')
sys.modules['myglobals'].__dict__.update({'first': 'thing', 'second': 'thing'})

import myglobals
print(myglobals.first) # prints 'thing'

Or if you've only got one global, how about this extremely dodgy approach:

import sys
sys.modules['myglobal'] = 'thing'

import myglobal
print(myglobal) # prints 'thing'