Defining a variable in a function python

Question

I have a function which has an if statement and asks for user input.

def my_function():
    answer = input(";")
    if condition 1
        a = 1
    else
        a = 0

I then want to run the function like so ''' my_funnction() ''' Then I want to extract the value of a based on the outcome of the function. When I try to do this it says the variable is undefined. When I define the variable, a, outside the function then its value doesn't change. How can I have the value of my variable be extracted from the function?

Return it from the function. A variable is local, by definition. Or put your function inside a class and declare the variable as an instance attribute of the class. — Óscar López, Oct 08 '22 at 10:32
You define the variable `a` and give it a value, but like all variables defined inside functions you throw it away (along with its value) once the function terminates. You can return values from functions using `return`, but the names of variables remain inaccessible. — quamrana, Oct 08 '22 at 10:36
Do you want to return the input value or only return `a` based on input was true or false? — Arifa Chan, Oct 08 '22 at 10:39

S.B · Answer 1 · 2022-10-08T10:46:20.860

Nobody has access to function's local namespace. a is only accessible during the execution of the my_function.

You should return the value from the function and then do whatever you want with it later:

def my_function():
    answer = input(";")
    if condition 1
        a = 1
    else:
        a = 0
    return a

a = my_function()

Another solution which I don't recommend is using global keyword:

def my_function():
    global a
    if True:
        a = 1
    else:
        a = 0

my_function()
print(a)

By saying so, you make changes in global namespace. That's why you can access it later. (You don't have to define it in global namespace first)

However with a simple search you can find hundreds of articles like this about why using global variables is not recommended and why functions should be isolated.

score 0 · Accepted Answer · answered Oct 08 '22 at 11:08

0

Here is the easiest way.

def my_function():
    answer = input(";")

    if condition 1
        my_function.a = 1 #just add the function name to the variable
    else
        my_function.a = 0 #here also

Then

print(my_function.a)

answered Oct 08 '22 at 11:08

UNK30WN

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Defining a variable in a function python

2 Answers2