title: Error: can only concatenate list (not "int") to list
body: <p>I am getting this error when I try to populate users First_Name in a csv file. Can someone show me what I am doing wrong</p>
  
  <pre><code> import csv
  
  # Define users 
  valid_input = False
  while not valid_input:
      users =raw_input('Number of users: ')
      try:
          users = range(0,int(users))
          valid_input = True
      except:
          print "Invalid input"
          pass
  
  First_Name = ["Test"+str(user) for user in  range (1, users+1)]
  Last_Name = ["User%s" %user for user in users]
  Email_Addresses = []
  for user in users:
      email= raw_input("Email domain for user %d: " %user)
      Email_Addresses.append(Last_Name[user] + email)
  Password = ["Password1" for user in users]
  Group =["Test" for user in users]
  Admin = ["Yes" for user in users]
  # open a file for writing.
  # open a file for writing.
  with open('users.csv', 'wb') as csv_out:
      writer = csv.writer(csv_out)
      writer.writerows(zip(Email_Addresses, Password, First_Name, Last_Name, Group, Admin))
  </code></pre>
  
  <p>This is the Traceback I am getting
      Traceback (most recent call last):
         First_Name = ["Test"+str(user) for user in  range (1, users+1)]
      TypeError: can only concatenate list (not "int") to list</p>