Protcol Buffers - Python - Issue with tutorial
Question: **Context**

  * I'm working through this tutorial: <https://developers.google.com/protocol-buffers/docs/pythontutorial>
  * I've created files by copy and pasting from the above tutorial

**Issue**

When I run the below file in `python launcher`nothing happens:

    
    
    #! /usr/bin/python
    
    import addressbook_pb2
    import sys
    
    # Iterates though all people in the AddressBook and prints info about them.
    def ListPeople(address_book):
      for person in address_book.person:
        print "Person ID:", person.id
        print "  Name:", person.name
        if person.HasField('email'):
          print "  E-mail address:", person.email
    
        for phone_number in person.phone:
          if phone_number.type == addressbook_pb2.Person.MOBILE:
            print "  Mobile phone #: ",
          elif phone_number.type == addressbook_pb2.Person.HOME:
            print "  Home phone #: ",
          elif phone_number.type == addressbook_pb2.Person.WORK:
            print "  Work phone #: ",
          print phone_number.number
    
    # Main procedure:  Reads the entire address book from a file and prints all
    #   the information inside.
    if len(sys.argv) != 2:
      print "Usage:", sys.argv[0], "ADDRESS_BOOK_FILE"
      sys.exit(-1)
    
    address_book = addressbook_pb2.AddressBook()
    
    # Read the existing address book.
    f = open(sys.argv[1], "rb")
    address_book.ParseFromString(f.read())
    f.close()
    
    ListPeople(address_book)
    

**Result:**

![enter image description here](http://i.stack.imgur.com/EI8IT.png)

**Question**

  * What steps should I take to work out the issue?


Answer: That's not "nothing happens". You got an error message showing that you didn't
call the program correctly. Specifically, you didn't pass it an address book
file to use.

