Why does my function not return value to global variable?

Question

Why does print(squared) return 0 instead of 100?

I thought that after being returned from the function – the value of the variable squared would be assigned to the the global variable with the same name?

squared = 0
def square(n):
    """Returns the square of a number."""
    squared = n**2
    print "%d squared is %d." % (n, squared)
    return squared


square(10)
print(squared)

returns:

Asked By: ruben_KAI

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Source

Answer 1

Essentially what is happening here is you are creating a local variable in the square function. To change squared, simply type:

squared =square(10)
print squared

Answered By: John

Answer 2

Assign the result of the function to the variable:

squared = square(10)

This is the whole point of using return squared in the function, isn’t it?

Answered By: Barmar

Answer 3

The function square never changes the variable squared that is found in the global scope. Inside the function you declare a local variable with the same name as the global variable, this however will change the local variable and not the global variable. Then when you print(squared) you are printing that unchanged global variable which is still 0 as you initially set it. As a matter of code cleanliness you really should try to avoid having local variables and global variables sharing the same name as it causes confusion (as we have seen in this question) and makes the code much harder to read.

To change the global variable from within a function you must tell Python to do so by using the global keyword to make the name refer to the global variable. You might want to look at this question: Use of "global" keyword in Python

The easier and better option of course is just to use the return value of the function. Minimizing the use of global mutable state is a good goal.

Answered By: shuttle87

Answer 4

Sort of. Your very close. You need to change the following:

def square(n):
    """Returns the square of a number."""
    squared = n**2

To:

def square(n):
    """Returns the square of a number."""
    global squared

    squared = n**2

Hope this helps!

Answered By: Vale Tolpegin

Why does my function not return value to global variable?

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