CODEWITHSUNDEEP
pythonstringprinting
Danny Garcia
Danny Garcia

Reputation: 227

Python "none" printing

I'm writing out this program with the hopes of getting this output: 

True
True
False
False

and I'm getting it with "none" printed in between my expected output:

True
None
True
None
False
None
False
None

I have no idea why these "none" strings are printing, any help would be greatly appreciated! Here is my code: 

# function:   check_answer
# input:      two numbers (number1 & number2, both integers); an answer (an integer)
#             and an operator (+ or -, expressed as a String)
# processing: determines if the supplied expression is correct.  for example, if the operator
#             is "+", number1 = 1, number2 = 2 and answer = 3 then the expression is correct
#             (1 + 2 = 3).
# output:     returns True if the expression is correct, False if it is not correct

def check_answer (number1, number2, answer, operator):
    if operator == "+":
        test = number1 + number2
        if test == answer:
            print ("True")
        else:
            print ("False")
    if operator == "-":
        test2 = number1 - number2
        if test2 == answer:
            print ("True")
        else:
            print ("False")
    return

answer1 = check_answer(1, 2, 3, "+")
print (answer1)
answer2 = check_answer(1, 2, -1, "-")
print (answer2)
answer3 = check_answer(9, 5, 3, "+")
print (answer3)
answer4 = check_answer(8, 2, 4, "-")
print (answer4)

Thanks so much!!

Upvotes: 0

Views: 92

Answers (1)

alecxe
alecxe

Reputation: 473813

This is because of the print(answer1) like calls - your function returns nothing which is why you see None printed. Just don't print what your function returns:

check_answer(1, 2, 3, "+")
check_answer(1, 2, -1, "-")
check_answer(9, 5, 3, "+")
check_answer(8, 2, 4, "-")

Or, return True/False from the function and print the result:

def check_answer(number1, number2, answer, operator):
    if operator == "+":
        test = number1 + number2
        return test == answer
    if operator == "-":
        test2 = number1 - number2
        return test2 == answer

answer1 = check_answer(1, 2, 3, "+")
print (answer1)
answer2 = check_answer(1, 2, -1, "-")
print (answer2)
answer3 = check_answer(9, 5, 3, "+")
print (answer3)
answer4 = check_answer(8, 2, 4, "-")
print (answer4)

As a side note, you can simplify your function by using the operator module and mapping the operation strings into actual operations. Working sample for + and -:

from operator import add, sub

def check_answer(number1, number2, answer, operator):
    operations = {
        "+": add,
        "-": sub
    }
    if operator not in operations:
        raise ValueError("Operator '%s' not supported" % operator)

    return operations[operator](number1, number2) == answer

Upvotes: 1

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