TypeError: can only concatenate tuple (not "int") in Python

Question

I am going to need your help with this constant tuple error I keep getting. Seems that it is a common mathematical error that many have. I have read almost every instance of TypeError including 'not int', 'not list', 'not float' etc. Yet I have failed to figure out why I get it.

I have written the below code that allows you to enter the sum of random number and in the end it calculates your success ratio. So I have a counter "right=right+1" to count my correct answers. Seems as if Python doesn't like that.

Here is what I have written:

import random 
#the main function
def main():
    counter, studentName, averageRight, right, answer, number1, number2 = declareVariables() 
    studentName = inputNames()

    while counter < 10:
        number1, number2 = getNumber()
        answer = getAnswer(number1, number2, answer)
        right = checkAnswer(number1, number2, answer, right)
        counter = counter + 1
    results(right, averageRight)
    displayInfo(studentName, right, averageRight)

def declareVariables():
    counter = 0
    studentName = 'NO NAME'
    averageRight = 0.0
    right = 0.0
    answer = 0.0
    number1 = 0
    number2 = 0
    return counter, studentName, averageRight, right, answer, number1, number2

def inputNames():
    studentName = raw_input('Enter Student Name: ')
    return studentName

def getNumber():
    number1 = random.randint(1, 500)
    number2 = random.randint(1, 500)
    return number1, number2

def getAnswer(number1, number2, answer):
    print 'What is the answer to the following equation'
    print number1
    print '+'
    print number2
    answer = input('What is the sum: ')
    return answer

def checkAnswer(number1, number2, answer, right):
    if answer == number1+number2:
        print 'Right'
        right = right + 1
    else:
        print 'Wrong'

    return right, answer

def results(right, averageRight):
    averageRight = right/10
    return averageRight



def displayInfo(studentName, right, averageRight):
    print 'Information for student: ',studentName
    print 'The number right: ',right
    print 'The average right is: ', averageRight

# calls main
main()

and I keep getting:

Traceback (most recent call last):
  File "Lab7-4.py", line 70, in <module>
    main()
  File "Lab7-4.py", line 15, in main
    right = checkAnswer(number1, number2, answer, right)
  File "Lab7-4.py", line 52, in checkAnswer
    right = right + 1
TypeError: can only concatenate tuple (not "int") to tuple Press any key to continue . . .

Answer 1

Your checkAnswer() function returns a tuple:

def checkAnswer(number1, number2, answer, right):
    if answer == number1+number2:
        print 'Right'
        right = right + 1
    else:
        print 'Wrong'

    return right, answer

Here return right, answer returns a tuple of two values. Note that it's the comma that makes that expression a tuple; parenthesis are optional in most contexts.

You assign this return value to right:

right = checkAnswer(number1, number2, answer, right)

making right a tuple here.

Then when you try to add 1 to it again, the error occurs. You don't change answer within the function, so there is no point in returning the value here; remove it from the return statement:

def checkAnswer(number1, number2, answer, right):
    if answer == number1+number2:
        print 'Right'
        right = right + 1
    else:
        print 'Wrong'

    return right

Answer 2

right = checkAnswer(number1, number2, answer, right)

You are assigning what is returned by checkAnswer. But you are returning a tuple from it.

return right, answer

So, after the first iteration right becomes a tuple. And when it reaches

right = right + 1

the second time, it fails to add an int to a tuple.