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I am learning python and am currently writing a simple program that has to be divided into functions. My problem is that I have one function that should return strings for four different variables, that then should be used in another function.

E.g.

def function1():
   var1 = input("Write something: ")
   var2 = input("Write something: ")
   var3 = input("Write something: ")

def function2():
   print(var1)
   print(var2)
   print(var3)

function1()
function2()

This gives an error message since var1 is not defined in the frame of function2. How should this be solved? The illustration is very simplified for clarity, but I could post something more specific if required.

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  • 1
    @AvinashRaj really, we shouldn't be teaching people to use globals, if it can be avoided. I'm a bit surprised to see you, of all people, do that. Are you having a sarcastic day? Commented Feb 8, 2016 at 13:01
  • 1
    @David Return a list, dictionary or tuple of three values and pass them as three arguments into the second function... Commented Feb 8, 2016 at 13:01
  • This is really extremely basic. You're better off studying some basic python (or any programming language that uses functions, for that matter.) Commented Feb 8, 2016 at 13:03

4 Answers 4

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6

Return the variables in function1:

def function1():
    var1 = input("Write something: ")
    var2 = input("Write something: ")
    var3 = input("Write something: ")
    return var1, var2, var3

and make them arguments in function2:

def function2(var1, var2, var3):
    print(var1)
    print(var2)
    print(var3)

Call them like this:

var1, var2, var3 = function1()
function2(var1, var2, var3)
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Comments

1

That's not what functions are for.

There is a thing called scoping, which basically says that variables declared within a function are local to that function and can't be accessed by anything else. If you need to pass values to a function, use parameters.

This should all be covered by the Python introduction you're probably currently reading -- just read on one or two pages :)

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2 Comments

The point of using functions in this exercise was to break down the program into smaller sub-programs. My problem was that in the example in the course the function only needed to return one value, whereas in the exercise you need to return 4 different values using almost the same function (meaning creating 4 different functions would kind of remove the point of having functions since nothing would be simplified). The course showed me how to use a return value from a function, but not if it was possible to have several return functions so that's why I was wondering.
The point of using functions in this exercise was to break down the program into smaller sub-program Exactly, and the point of that is to consider your function as isolated thing, which takes input and generates output, but doesn't access the state of the calling function. So write a function that takes var1,var2 and var3 as parameters!
1

Correct approach would be to return values from functions and pass them via input arguments:

def function1():
    var1 = input("Write something: ")
    var2 = input("Write something: ")
    var3 = input("Write something: ")
    return var1, var2, var3


def function2(a, b, c):
    print(a)
    print(b)
    print(c)

v1, v2, v3 = function1()
function2(v1, v2, v3)

I renamed some of parameters to emphasize that there is no name relation anywhere. All values are explicitly returned and explicitly passed.

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0

With your current example the better approach is reuse the same functions three times:

def function1():
    return input("Write something: ")

def function2(var):
   print(var)

for i in range(0, 3):
    var = function1()
    function2(var)

But it may be better return the variables in function1 and then pass it to function2.

def function1():
   var1 = input("Write something: ")
   var2 = input("Write something: ")
   var3 = input("Write something: ")
   return var1, var2, var3

def function2(var1, var2, var3):
   print(var1)
   print(var2)
   print(var3)

var1, var2, var3 = function1()
function2(var1, var2, var3)

It depends on your specific problem.

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