Dictionaries

Dictionaries

A dictionary is a data type similar to arrays, but works with keys and values instead of indexes. Each value stored in a dictionary can be accessed using a key, which is any type of object (a string, a number, a list, etc.) instead of using its index to address it.

For example, a database of phone numbers could be stored using a dictionary like this:
phonebook = {}
phonebook["John"] = 938477566
phonebook["Jack"] = 938377264
phonebook["Jill"] = 947662781

Alternatively, a dictionary can be initialized with the same values in the following notation:
phonebook = {
    "John" : 9384xxx66,
    "Jack" : 9383xxx64,
    "Jill" : 9476xxx81
        }
Removing a value

To remove a specified index, use either one of the following notations:
del phonebook["John"]
#OR
phonebook.pop("John")
Iterating over dictionaries

Dictionaries can be iterated over, just like a list. However, a dictionary, unlike a list, does not keep the order of the values stored in it. To iterate over key value pairs, use the following syntax:
phonebook = {}

phonebook["John"] = 9384xxx66
phonebook["Jack"] = 9383xxx64
phonebook["Jill"] = 9476xxx81
for name, number in phonebook.iteritems():
    print "Phone number of %s is %d" % (name, number)

           

     
PreviousNext