Python 2.6 unittest - how to set a value to use for a global variable in a function that you're testing

Question

I'm having trouble setting the value of a global variable in a function that I'm writing for unit tests.

The function is probably not ready to be used in a test. Or at least to be used to test in an easy manner, but I'm trying to work around that.

Here is an example of the function I'm trying to test:

def my_func_with_globals(filepath):
  spos=filepath.find(__my_global_var1)
  new_path = filepath[0:spos] + __my_global_var2
  return new_path

def some_function():
  ...
  my_func_with_globals(filepath)
  ...

if __name__ = '__main__':
  global __my_global_var1
  __my_global_var1='value1'  
  global __my_global_var2
  __my_global_var2='value2'
  ...
  some_function()

And here is an example of my test:

import unittest
from my_module import *

class UnitTestMyModule(unittest.TestCase):
  def test_my_func_with_globals(self):
    self.assertEqual(my_func_with_globals('arbitrary/file/path'), 'valid output')

Another example of my test using @kdopen's suggestion (gives me the same error):

import unittest
import my_module

class UnitTestMyModule(unittest.TestCase):
  def test_my_func_with_globals(self):
      my_module.__my_global_var1='some/value'
      my_module.__my_global_var2='second_val'
      self.assertEqual(my_module.my_func_with_globals('arbitrary/file/path'), 'valid output')

I keep getting the error:

NameError: global name '__my_global_var1' is not defined.

I've tried a few different things, but I can't get anything to work. Using unittest.mock.patch looks like it would work perfectly, but I'm stuck with what I currently have with v2.6.4.

kdopen · Accepted Answer · 2016-08-11 20:24:23Z

1

The globals are defined with a double leading underscore, so they are not imported by the from my_module import * statement.

You can make them accessible with the following:

from my_module import __my_global_var1, __my_global_var2

Alternatively, if you used import my_module you can access them as my_module.__my_global_var1 etc.

But I don't see any reference to the global variables in your sample test case

Here's a simple example

a.py

__global1 = 1

def foo():
    return __global1

b.py:

import a

print "global1: %d" % a.__global1
print "foo: %d" % a.foo()
a.__global1 = 2
print "foo: %d" % a.foo()

And running b.py

$ python2.6 b.py 
global1: 1
foo: 1
foo: 2

UPDATE:

Dang it, missed the obvious

You declare the variables within the if test. That code doesn't run on import - only when you execute python my_module from the command line.

During importing, __name__ will be set to my_module, not __main__

So, yes - they are undefined when you call your unit test.

edited Aug 11, 2016 at 20:24

answered Aug 11, 2016 at 18:50

kdopen

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5 Comments

user797963 Over a year ago

I've actually tried doing 'import my_module' and then setting the values to use in my test with my_module.__my_global_var1 and my_module.__my_global_var2, and I still get the same error 'NameError: global name '__my_global_var1' is not definted'

kdopen Over a year ago

then it seems there's something else going on ... are the globals actually defined in my_module or does it import something else (or perhaps they're in the __init__.py)

kdopen Over a year ago

have added working code, explicitly run using python v2.6 ... though it is v2.6.9

kdopen Over a year ago

And I've just added the real problem with your code ;)

user797963 Over a year ago

lol, good catch! I completely didn't realize that __name__ would be set to my_module, not __main__ on import. I set the global vars in the if test as my_module.__my_global_var1and the world is right again. Great explanation btw!

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