[Tutor] Adding items to dictionaries

[Jon Moore]

Hi,

I have the following dictionary:

pairs = {"Jon Moore": ["Tony Moore", "Stanley Moore"],
         "Simon Nightingale": ["John Nightingale", "Alan Nightingale"],
         "David Willett": ["Bernard Willet", "Robert Willet"],
         "John Jackson": ["John Jackson", "Peter Jackson"],
         "James Southey": ["Richard Southey", "Paul Southey"],
         "Shaun Forsythe": ["William Forsythe", "Angus Forsythe"],
         "Daniel Geach": ["Mike Geach", "Andy Geach"]}

Where the names represent a son, father and grandfather.

I am trying to add a new term and related definitions to the dictionary, but
my code does not seem to work:

        son = raw_input("Please enter the name of the Son: ")
        if son not in pairs:
            father = raw_input("Who is the Father?: ")
            grandfather = raw_input("What is the Grand Father?: ")
            pairs[son][0] = father
            pairs[son][1] = grandfather
            print "\n", son, ",", father, "and" ,grandfather, "have been
added."
        else:
            print "\nThat Son already exists!"

The error I get is:

Please enter the name of the Son: Steven Bates
Who is the Father?: Alan Bates
What is the Grand Father?: Master Bates
Traceback (most recent call last):
  File "C:\Documents and
Settings\Administrator\Desktop\FOO\transfer\whos_your_daddy_and_grandaddy.py",
line 65, in ?
    pairs[son][0] = father
KeyError: 'Steven Bates'
>>>

Where am I going wrong?
--
Best Regards

Jon Moore
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