test.py
```
def test_normal(val):
  val = 2

def test_list(lst):
  lst[0] = 3

a = 1
test_normal(a)
print a

b = [1]
test_list(b)
print b
```
Results
```
1
[3]
```
@Nathan Does this sample code help you? For more detail, see http://stackoverflow.com/questions/986006/python-how-do-i-pass-a-variable-by-reference