Python 3, Passing data from one function to another

Question

def main():
    uInput()
    calc()
def uInput():
    value1 = int(input('Please put in the first number'))
    value2 = int(input('Please put in your second number'))
    return value1
    return value2
def calc(value1,value2):    
    finalNumber = value1 + value2
    print (finalNumber)
main()

I am messing around with python, and am trying to make a simple calculator program. I'm trying to pass the input values from the uInput module, to the calc module. It keeps saying missing two required position arguments. Can you only pass one variable from a module to another module?

As a side note, `uInput` and `calc` are _functions_. Modules are a different thing, and when you get farther into the language and start `import`ing things, you will get confused if you mix them up. — abarnert, Nov 13 '13 at 19:40

score 6 · Accepted Answer · answered Nov 13 '13 at 19:32

A function exits at the first return statement it encounters, so return value2 is never reached. To return multiple values use a tuple:

return value1, value2     #returns a tuple

Assign the returned value from uInput() to variables inside main:

val1, val2 = uInput()  #Assign using sequence unpacking

Pass these variables to calc:

calc(val1, val2)

Corrected version:

def main():
    val1, val2 = uInput()
    calc(val1, val2)

def uInput():
    value1 = int(input('Please put in the first number'))
    value2 = int(input('Please put in your second number'))
    return value1, value2

def calc(value1,value2):    
    finalNumber = value1 + value2
    print (finalNumber)
main()

wvdz · Answer 2 · 2013-11-13T19:32:22.223

1

Basically, a function can only return once. When you use the return statement, the flow literally "returns", so the second return in your code is unreachable.

However, in python, you can return multiple values as a "tuple":

return value1,value2

edited Nov 13 '13 at 19:32

answered Nov 13 '13 at 19:30

wvdz

16,251
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score 1 · Answer 3 · answered Nov 13 '13 at 19:31

1

You can return two things at once from any function, but you can only use one return statement. by using return x, y this returns a tuple (x, y), which you can use in your main function.

def uInput():
    value1 = int(input('Please put in the first number'))
    value2 = int(input('Please put in your second number'))
    return value1, value2 # this returns a tuple

def main():
    val1, val2 = uInput() # unpack the tuple values into two variables
    calc(val1, val2)

answered Nov 13 '13 at 19:31

jramirez

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Is it possible to return three values? – user2832472 Nov 15 '13 at 19:17
yes and the same principle applies. you will need `val1, val2, val3 = ` – jramirez Nov 15 '13 at 19:29

score 0 · Answer 4 · edited Oct 13 '17 at 12:10

def uInput():
    value1 = int(input('Please put in the first number'))
    value2 = int(input('Please put in your second number'))
    return value1, value2             # this returns a tuple

def calc(value1,value2):    
    finalNumber = value1 + value2
    print (finalNumber)

def main():
    val1, val2 = uInput()   # unpack the tuple values into two variables
    calc(val1, val2)     # this is one method which uses two temporary variables

    # ALternatively you can use python's argument unpacker(*) to unpack the tuple in the function call itself without using any temporary variables.

    calc(*uInput())

For more details check out http://docs.python.org/tutorial/controlflow.html#unpacking-argument-lists

Python 3, Passing data from one function to another

4 Answers4