Local (?) variable referenced before assignment

Question

test1 = 0
def test_func():
    test1 += 1
test_func()

I am receiving the following error:

UnboundLocalError: local variable 'test1' referenced before assignment.

Error says that 'test1' is local variable but i thought that this variable is global

So is it global or local and how to solve this error without passing global test1 as argument to test_func?

I received the same error but in my case it turned out to be an indentation problem. The code I was modifying was indented with spaces, but my editor was indenting with tabs. Dumb mistake on my part, and not at all the problem you had, but I hope to save someone out there some time by commenting here -- this was the first hit in my Google search. — Josh, Aug 15 '17 at 19:19

score 282 · Accepted Answer · edited Sep 08 '22 at 10:16

282

In order for you to modify test1 while inside a function you will need to do define test1 as a global variable, for example:

test1 = 0
def test_func():
    global test1 
    test1 += 1
test_func()

However, if you only need to read the global variable you can print it without using the keyword global, like so:

test1 = 0
def test_func():
    print(test1)
test_func()

But whenever you need to modify a global variable you must use the keyword global.

edited Sep 08 '22 at 10:16

Karl Knechtel

answered Aug 10 '12 at 15:43

Florin Stingaciu

24

Wow, this is such an *ahem* *ahem* odd language design decision. – Moff Kalast Nov 15 '18 at 17:36

score 64 · Answer 2 · answered Aug 10 '12 at 15:45

64

Best solution: Don't use globals

>>> test1 = 0
>>> def test_func(x):
        return x + 1

>>> test1 = test_func(test1)
>>> test1
1

answered Aug 10 '12 at 15:45

jamylak

12

Totally agree, you don't know how global can mess up with the code later :) – Jim Raynor Oct 29 '15 at 03:14
so you dont modify it inside of function but create new temp variable ? – Qbik Apr 27 '21 at 09:33

score 12 · Answer 3 · edited Jul 12 '22 at 09:49

12

You have to specify that test1 is global:

test1 = 0
def test_func():
    global test1
    test1 += 1
test_func()

edited Jul 12 '22 at 09:49

Neuron

answered Aug 10 '12 at 15:41

Stanislav Heller

3 Answers3