title: int() argument must be a string or a number, not 'tuple'
body: <p>This is my coding:</p>
  
  <pre><code>#Getting them to import their code:
  number = int(input("Enter 7 digit GTIN code to get eighth number : "))
  
  #importing math for subtracting later:
  import math
  
  #Getting the numbers X3 &amp; X1 and then adding them:
  def eight(total):
      multiplier = [3, 1]
      total = 0
      for i, digit in enumerate(str(number)):
          total = total + int(digit)*multiplier[i%2]
  
  #Subtracting the total to get the last number:
          nearest_10 = int(math.ceil(total / 10.0)) * 10
          return nearest_10 - total
  
  
  code = number,eight(number)
  code = int(code)
  print(code)
  
  #printing their full number:
  
  
  
  #Checking the validity of the eight digit GTIN-8 code:
  
  def validity(valid):
      multiplier = [3, 1]
      valid = 0
      string = ""
      for i, digit in enumerate(list(str(code))):
           valid = valid + str(digit)*multiplier[i%2]
           string = string+str(str(digit)*multiplier[i%2])+", "
  
      if code % 10 == 0:
          print"Valid"
      else:
          print"Not valid"
  </code></pre>
  
  <p>However when I am trying to convert my code to an integer for later, as it needs to be a single integer for the answer, it says this:     </p>
  
  <pre><code>code = int(code)
  TypeError: int() 
  argument must be a string or a number, not 'tuple'
  </code></pre>