从modulename.main（）方法访问时，如何使变量可从另一个python脚本访问

Question

I have a simple python script which invokes the main function of another python script. Something like this:

invoker_code.py :

import os
invoked_code = '/tmp/invoked_code.py'
import sys
if os.path.exists(invoked_code):
    sys.append(invoked_code)
else:
    sys.exit(1)
import invoked_code
__data_bag = { 'var' : 'value' }
invoked_code.main()

/tmp/invoked_code.py :

def main():
    print '%s' %(__data_bag['var'])

I want the invoked_code to be able to access the variable __dict_bag from within its code base. This should be achieved with minimal or zero code changes on the invoked_code.py script as this is a third party script and I do not have write access to this script. How can I do that?

Answer 1

Modules can access and modify each other's global variables:

module1.py :

foobar = [1, 2, 3]
def main():
    print foobar[0]
def printx():
    print x

module2.py :

import module1
print module1.foobar
module1.main()
module1.foobar[0] = 100
module1.main()
module1.x = "exex"
module1.printx()

Running module2.py :

[1, 2, 3]
1
100
exex

Note that you can both modify a global variable in the other module, and also create one. However, I would instead recommend doing as poke said and passing the variable into the invoked function.

Answer 2

The main function in invoked_code will look up the __data_bag name within its own scope. So it will first try to find it inside of the function itself and then go up to module level, ie what's defined in the invoked_code.py .

As __data_bag does not exist in either places, the function won't be able to find it. So to solve this without changing the invoked_code , you need to supply the data to a place where the function will look at. The only place you have access to is the module though, so that's the only thing you can do:

import invoked_code
invoked_code.__data_bag = { 'var' : 'value' }
invoked_code.main()

Note that this is really not a good way to solve this problem though. The proper way to solve this would be to have the main function accept a parameter for this:

def main(data_bag):
    print '%s' %(data_bag['var'])

Then you could simply pass the value in your invoking script:

invoked_code.main(__data_bag)