Use global variables in other functions doesn't work

Question

This is a simplified example of my problem. I need to use a variable which I have created in another function, but putting global before the variable instantiation doesn't work.

x = 10
def one():
    global x
    a = x +2
    b = a/2
    print (b)
def two():            
    one()             
    c = int(input())            
def three():
    global a
    global c           
    d = c + a         
    print(b)

two()         
three()

If you `return` the value from the function then you can use it outside of the function itself. — Nick Parsons, Nov 25 '18 at 11:32
Well, if you want these variables to be global, you should _make_ them global - define them in the outer scope. — ForceBru, Nov 25 '18 at 11:32
duplicate: https://stackoverflow.com/questions/423379/using-global-variables-in-a-function — SuperShoot, Nov 25 '18 at 12:17

Rafael · Answer 1 · 2018-11-25T12:00:00.817

To use a global variables in Python you need to declare them as such:

x = 10

def one():
    global x
    global a
    global b
    a = x +2
    b = a/2
    print (b)

def two():            
    one()             
    global c
    c = int(input())            

def three():
    global a
    global c           
    d = c + a         
    print(d)
    print(b)

two()       
three()

In Python, a variable defined on top of the file (not within a function, an if statement etc) is considered as a global variable and is accessible throughout the file (in other functions etc) but also to any file importing that file.

A variable defined in a scope other than the main body (say a function) it's accessible to that function only. In this case, if you define a new variable within a body other than the main body, you need to tell Python that this variable is global just before you create the variable. Similarly, if you need to access a global variable, you need to use global var just before you try to access it.

Not the best implementation. I will recommend, as others already did, to use a class or functions with arguments and returns instead.

Thank you very much. You really helped me. Have a nice day. – guverner2 Nov 25 '18 at 11:58 — guverner2, Nov 25 '18 at 11:58

score 0 · Answer 2 · answered Nov 25 '18 at 11:33

Use the return statement and function parameters:

x = 10
def one(x):
    a = x +2
    b = a/2
    print(b)
    return a, b

def two():                        
    c = int(input()) 
    return c    

def three(a, b, c)                 :         
    d = c + a         
    print(b)

a, b = one(x)
c = two()         
three(a, b, c)

score -1 · Answer 3 · answered Nov 25 '18 at 11:34

-1

You could try to move these three functions into some class, create an 'x' attribute in this class, and then use this 'x' in the functions above as self.x

answered Nov 25 '18 at 11:34

Artyom Gilevich

1

Use global variables in other functions doesn't work

3 Answers3