use global reference inside nested functions

Question

I got an error at the while, that the name 'start' is not defined, although I declared it as global inside the nested one, I know that there is another approach is to changed the signature of the function of BS to take the start and end variables, but I need to know how to solve it using the global approach, Thanks!

class math:
    def search(self,nums,x):
        start = 0
        end = len(nums)

        def BS():
            global start
            global end

            while(start<=end):
                #i assign  here  a new value to start and end

        first = BS()
        return first

dvlper · Accepted Answer · 2020-05-19 01:18:30Z

5

Use nonlocal, so something like:

class math:
    def search(self,nums,x):
        start = 0
        end = len(nums)

        def BS():
            nonlocal start
            nonlocal end

            while(start<=end):
                pass # use pass if you want to leave it empty!
                #i assign  here  a new value to start and end

        first = BS()
        return first

Maybe you'll find this helpful!

answered May 19, 2020 at 1:18

dvlper

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4 Comments

Daniel Walker Over a year ago

Exactly. @Flupper, the reason this works is because, when you first defined start, Python treated it as local to the search function. When, in the BS function, you declared global start, Python assumed that this must be a different variable from the previous instance of start because that one wasn't global.

Flupper Over a year ago

Thank you guys, finally got it, it took me some time to know this reason.

dvlper Over a year ago

@Flupper Do you mind accepting the answer if it helps! Thanks

Flupper Over a year ago

I immediately accepted it after you submitted the answer, but I got an error message that I should wait more time to accept it, then I forgot, thank you for remembering me it!

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