global var becomes local --UnboundLocalError: local variable referenced before assignment

Question

I initialized rate as a global var:

import os, sys
rate=30

def foo():
    print('#########rate:', rate)
    if False:
        rate=int(sys.argv[2])


foo()

but when running the script, I get the following error:

Traceback (most recent call last):
  Line 10, in <module>
    foo()
  Line 5, in foo
    print('#########rate:', rate)
UnboundLocalError: local variable 'rate' referenced before assignment

although the if False: rate=int(sys.argv[2]) statement is not executed, it seems has some influence, is there some python rules explains this?

falsetru · Accepted Answer · 2013-09-01 15:53:21Z

3

You should declare rate as global:

import os, sys
rate=30

def foo():
    global rate # <----
    print('#########rate:', rate)
    if False:
        rate=int(sys.argv[2])


foo()

If there is assignment to a varaint (without global declaration), it is treated as local variable.

edited Sep 1, 2013 at 15:53

answered Sep 1, 2013 at 14:21

falsetru

371k69 gold badges769 silver badges659 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Ben Over a year ago

Might be worth explaining why

zhangxaochen Over a year ago

why it becomes local even that expression is not executed?

falsetru Over a year ago

@zhangxaochen, If there is assignment to a varaint (without global declaration), it is treated as local variable.

Collectives™ on Stack Overflow

global var becomes local --UnboundLocalError: local variable referenced before assignment

1 Answer 1

3 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Related