Definition variable not found

Question

I'm rather new to Python and trying to create several different definitions that run each other and refer to different variables in each. Could someone help me as to why this code doesn't work like this and what I need to change to make it work?

From what I thought, it defined what the variable testing was in the test1 definition and then it would pull that in the test2 and run in the run_this...

Python 2.7.9 (v2.7.9:648dcafa7e5f, Dec 10 2014, 10:10:46) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> def test1():
...     testing = 1
... 
>>> def test2():
...     print testing
... 
>>> def run_this():
...     test1()
...     test2()
... 
>>> run_this()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in run_this
  File "<stdin>", line 2, in test2
NameError: global name 'testing' is not defined
>>>

possible duplicate of [name not found globally code error](http://stackoverflow.com/questions/19568703/name-not-found-globally-code-error) — tripleee, Feb 18 '15 at 08:10

score 4 · Accepted Answer · answered Feb 18 '15 at 08:08

4

Your testing variable is scoped to test1(). In Python, variables defined inside functions are local to that function - no other functions or operations can access them.

When test2() tries to print from some variable called testing, it first checks for variables defined inside test2(). If it doesn't find a match, Python looks in the rest of the script for a match - since it's a scripting language, you could have defined testing outside both functions, in which case you'd get the behavior you're expecting. Since there isn't anything in the global scope, Python raises a NameError, letting you know that it can't find anything named testing inside test2().

answered Feb 18 '15 at 08:08

derekerdmann

17,696
11
76
110

So if I made this script into a module, would I then be able to call it like `def test2(): print test1.testing`? – double_j Feb 18 '15 at 08:12
1

@double_j - Not really. Take a look at this question and its top accepted answer for another good explanation of Python's scoping rules: http://stackoverflow.com/questions/291978/short-description-of-python-scoping-rules – derekerdmann Feb 18 '15 at 08:14
@double_j - `test1()` is still a function, and `test2()` still would not be able to access variables inside it. If you had defined `testing` outside the function, it would be accessible, but global variables should be avoided as much as possible. – derekerdmann Feb 18 '15 at 08:18
I get it now, I read that post you mentioned and it makes a lot more sense! I just need to re-write my whole script... :/ I totally thought definitions worked a little differently, but that's why I'm still learning – double_j Feb 18 '15 at 08:21

guidot · Answer 2 · 2015-02-18T10:05:20.497

Your code can be easily fixed by changing testing to a global variable:

testing = 7

def test1():
    gobal testing
    testing = 5

def test2():
    print(testing)

if __name__ = "__main__":
    test1()
    test2()

Note, that it is only required in routines doing write access to declare the variable as global, because otherwise a local variable with same name would be assigned and lost at procedure exit.

Definition variable not found

2 Answers2