Solving error: local variable 'counter' referenced before assignment

Question

Small question about globals. I have the following code:

counter = 0
class A():
    global counter

    def connect():
        counter += 1
        print("Opening connection",counter)
        # DO STUFF

    def disconnect():
        counter -= 1
        print("Closing connection",counter)
        # DO STUFF

Each time I connect or disconnect, I want to know the number of opened connections counter (not just for one instance, rather for all of the instances, so it should be static). But when running the code I get:

local variable 'counter' referenced before assignment

Why is that? Consider that A() is located in other file than main.

you don't need to write lobal counter in the class but you have to do it in the methods — Leonardo Scotti
– Leonardo Scotti, Commented Nov 22, 2020 at 10:03
@Michael Butscher, I know, in fact i edited, I made a mistake while writing — Leonardo Scotti
– Leonardo Scotti, Commented Nov 22, 2020 at 10:08

Safwan Samsudeen · Accepted Answer · 2020-11-22 10:05:31Z

3

As said in the comments, global declaration only works in a function or a method.

counter = 0
class A():
    def connect():
        global counter
        counter += 1
        print("Opening connection",counter)
        # DO STUFF

    def disconnect():
        global counter
        counter -= 1
        print("Closing connection",counter)
        # DO STUFF

answered Nov 22, 2020 at 10:05

Safwan Samsudeen

1,7172 gold badges13 silver badges28 bronze badges

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

2 Comments

vesii Over a year ago

Thank you. If I have two instances of A(), they share the counter right?

Safwan Samsudeen Over a year ago

Yup. P.S - This comment word limit is irritating.

Leonardo Scotti · Accepted Answer · 2020-11-22 10:06:28Z

1

You have to do this:

counter = 0
class A():

    def connect():
        global counter
        counter += 1
        print("Opening connection",counter)
        # DO STUFF

    def disconnect():
        global counter
        counter -= 1
        print("Closing connection",counter)
        # DO STUFF

answered Nov 22, 2020 at 10:06

Leonardo Scotti

1,08012 silver badges24 bronze badges

Comments

Granth · Accepted Answer · 2020-11-22 10:06:04Z

0

You should move global counter inside the functions.

Also if you are using multithreading/multiprocessing you should use a semaphore while updating the counter.

answered Nov 22, 2020 at 10:06

Granth

3942 gold badges6 silver badges21 bronze badges

Collectives™ on Stack Overflow

Solving error: local variable 'counter' referenced before assignment

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related