Unable to achieve global functionality in python

Question

So I am new to python and here is my python code:

def main():
    N = 1
    players = 10
    for _ in range(N):
        maxi = 0
        t1 = [3, 6, 7, 5, 3, 5, 6, 2, 9, 1]
        t2 = [2, 7, 0, 9, 3, 6, 0, 6, 2, 6]
        for i in range(players):
            count = t2[i]+1
            flag = 0
            def calcWin(count):
                global maxi,flag
                if(count in t1):
                    flag = 1
                    maxi = maxi + 1
                    t1.remove(count)
                else:
                    count = count + 1
                    if(count<=max(t1)):
                        calcWin(count)

            calcWin(count)
            print(flag)

main()

I want the variable 'maxi' to be accessible inside the function calcWin(). So it declared the variable as global inside the function. But it throws 'NameError'. I want the variable 'maxi' to reinitialize to 0 for each 'N'. Another thing is that the 'flag' variable always prints 0 even though it satisfies the condition 'if(count in t1)'. (Note: I declared 'flag' as global inside the function). Can somebody help me with this?

The general rule is to avoid global variables as much as possible. The code defines global variables in two nested loops, which brings a chaos — AlexMTX, Apr 14 '20 at 09:03
@AlexMTX Okay, then how can I achieve this without using global variables? — Kishan Lal, Apr 14 '20 at 09:04
@Kishan By passing the required values to the function and getting their updated values by return. — matheburg, Apr 14 '20 at 09:09
1/ The `maxi` and `flag` vars defined in your `main` functions are NOT globals - they are local to `main`. 2/ there's way too much code in your function, 3/ you don't need to re-define `calcWin` again and again in each iteration, 4/ there are mainly two ways to avoid globals: a/ passing values to and returning values from your functions and b/ use a class. — bruno desthuilliers, Apr 14 '20 at 09:11
Btw: If you want to use global variables in Python functions, you may refer to https://stackoverflow.com/questions/423379/using-global-variables-in-a-function — matheburg, Apr 14 '20 at 09:21

score 0 · Accepted Answer · answered Apr 14 '20 at 09:17

As you are asking in the comment for a way to do this without global variables, the following could be a proposal. Please understand that I just imitated what I think you intended with your original code. You may have to adapt your algorithm...

def main():
    n = 1
    players = 10
    for _ in range(n):
        maxi_persistent = 0
        t1 = [3, 6, 7, 5, 3, 5, 6, 2, 9, 1]
        t2 = [2, 7, 0, 9, 3, 6, 0, 6, 2, 6]
        for i in range(players):
            def calc_win(count, maxi):
                flag = False
                if count in t1:
                    flag = True
                    maxi += 1
                    t1.remove(count)
                else:
                    count += 1
                    if count <= max(t1):
                        return calc_win(count, maxi)
                return maxi, flag

            maxi_persistent, win_flag = calc_win(count=t2[i] + 1, maxi=maxi_persistent)
            print(win_flag)


if __name__ == "__main__":
    main()

Please note that flag, as you use it in your question, does not need any global handling. It is 0 at each call of the function, so I just set it to 0 (or False) in the beginning of the function instead.

Unable to achieve global functionality in python

1 Answers1