CODEWITHSUNDEEP
python
superloopnetworks
superloopnetworks

Reputation: 514

How to use a global variable in Python?

I'm not sure why it's not working when I declare a global variable...

first_read = True

def main():

    if (first_read == True):
        print "hello world"
        first_read = False

    print 'outside of if statement'

if __name__ == '__main__':
    main()

My traceback shows the following error:

Traceback (most recent call last):
   File "true.py", line 12, in <module>
      main()   
   File "true.py", line 5, in main
     if (first_read == True): 
UnboundLocalError: local variable 'first_read' referenced before assignment

Upvotes: 1

Views: 120

Answers (2)

Chuong Huynh
Chuong Huynh

Reputation: 84

In def main you should declare a global variable like this:

global first_read

this will use first_read as global variable in main function.

Upvotes: 2

Tisp
Tisp

Reputation: 436

You have to define variable as global:

first_read = True

def main():
    global first_read
    if (first_read == True):
       print "hello world"
       first_read = False

    print 'outside of if statement'

if __name__ == '__main__':
    main()

Upvotes: 3

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