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I am stuck on using variables defined in a previous function in another function. For example, I have this code:

def get_two_nums():
    ...
    ...
    op = ...
    num1 = ...
    num2 = ...
    answer = ...

def question():
    response = int(input("What is {} {} {}? ".format(num1, op, num2)))
    if response == answer:
        .....

How will I use the variables defined in the first function in the second function? Thank you in advance

Ben
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Matt
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  • Are you asking "how do I create variables in one function and have them be accessible in another function?"? Or are you asking "How do I evaluate the result of a mathematical equation where each component is stored as a string in its own separate variable?"? – Kevin Feb 11 '16 at 14:09
  • possible dupe: http://stackoverflow.com/q/423379/1561176 – Inbar Rose Feb 11 '16 at 14:17

3 Answers3

5

Variables are local to the functions; you need to return the relevant values you want to share to the caller and pass them to the next function that uses them. Like this:

def get_two_nums():
    ...
    # define the relevant variables
    return op, n1, n2, ans

def question(op, num1, num2, answer):
    ...
    # do something with the variables

Now you can call

question(*get_two_nums()) # unpack the tuple into the function parameters

or

op, n1, n2, ans = get_two_nums()
question(op, n1, n2, ans)
Tim Pietzcker
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3

Why not return a tuple?

def get_two_nums():
    ...
    ...
    op = ...
    num1 = ...
    num2 = ...
    answer = ...
    return op, num1, num2, answer

def question():
    op, num1, num2, answer = get_two_nums()
    response = int(input("What is {} {} {}? ".format(num1, op, num2)))
    if response == answer:
        # the rest of your logic here
TayTay
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2

You cannot simply pass them, because variables in get_two_nums are defined only in scope of get_two_numsfunction. So basically you have two options:

  1. Return their values as tuple into scope of another function as @TimPietzcker and @Tgsmith61591 proposed.

  2. Define variables within get_two_nums function as globals ( see global statement, for more info) as in code snipper below:

    def get_two_nums():
    global num1
    num1 = 'value1'
    global num2
    num2 = 'value2'
    global num3
    num3 = 'value3'

def question():
    # Call get_two_nums to set global variables for further using
    get_two_nums()
    response = int(input("What is {} {} {}? ".format(num1, num2, num3)))
    if response == answer:
        # Some code here ...

WARNING: Using global variables should be avoided, see Why are global variables evil? to get better idea of what i am talking about ...

Community
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Andriy Ivaneyko
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    It should be mentioned that using `global` should be avoided in most circumstances. Once your program grows in size, `global` can make problems very hard to debug. – Håken Lid Feb 11 '16 at 14:20
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    Surely you aren't advocating the use of `global`? This is a terrible practice. – AChampion Feb 11 '16 at 14:20
  • Guys you are definitely right and i am totally agree with you, i've update answer with this warning. However using global also gives possibility to get behaviour about which OP asked .... – Andriy Ivaneyko Feb 11 '16 at 14:24