Start here http://docs.python.org/tutorial/datastructures.html#dictionaries
Then here http://docs.python.org/library/stdtypes.html#mapping-types-dict
Then here http://docs.python.org/library/stdtypes.html#dict.get
characters.get( key, default )
key is a character
default is 0
If the character is in the dictionary, characters, you get the dictionary object.
If not, you get 0.
Syntax:
get(key[, default])
Return the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a KeyError.
