Using a variable defined outside a function in a def() statment

Question

I am working on a python thing and I assigned variable x*y to SecureNum. I then define a function in which I write: while R*S != SecureNum: it spits up the error that I am referencing SecureNum before assignment, even though it has been assignment earlier but not in the function. How can I fix this?

Thanks in advance! George

• abarnert: You probably don't actually want to do this. It's better to pass SecureNum as an argument, or to put the SecureNum variable and your function together in a class, etc. There are a lot of reasons to avoid avoid global variables.

Answer 1

Probably you are trying to assign to SecureNum later in that function

Because you haven't declared SecureNum to be global and Python sees you are assigning to it, it forces it to be a local variable.

SecureNum = 12345
def f(R, S):
 if R * S != SecureNum: #<== local SecureNum shadows the global one
 ...
 ...
 SecureNum = ... #<= This means SecureNum is a local 
def g(R, S):
 global SecureNum
 if R * S != SecureNum: #<== now this is the global SecureNum
 ...
 ...
 SecureNum = ... #<= and so is this one

This can be surprising because the problem isn't because really at the line where you are testing the value, it's because you are trying to rebind the name further down.

Answer 2

Use the following at the beginning of your function:

global SecureNum