Dictionaries 

A dictionary, like an array, is a collection of items; however, the items in a dictionary are referenced by strings called keys, rather than their order in a list. Another way to think of a dictionary is as a collection of key-value pairs, where the keys are used to retrieve the values.

To create a dictionary, use the following syntax where <key1>, <key2> are strings and value1, value2 are any values:

{<key1>:<value1>,<key2>:<value2>,<key3>:<value3>}

The following line will create a dictionary called d with two key-value pairs:

>> d = {"some_number": 1, "sup?": "yo!"}
>> print(d)

You can access a specific value of a dictionary using the following syntax:

<dictionary name>[<key>]

For example:

>> print(d["sup?"])
>> print(d["some_number"])

You can also set the value of a key by assigning a value to that key, as the following demonstrates:

>> d["some_number"] = 5
>> print(d["some_number"])

If you assign a value to a key that does not yet exist in a particular dictionary, the key will be added to the dictionary:

>> d["new_key"] = "I'm a new value"
>> print(d["new_key"])

On an intuitive level, the big advantage of Python dictionaries comes from the ability to store and reference items by key. It is easier to remember a name than a number. If, for example, you are working with a spreadsheet that has 100 columns, it is much more convenient to retrieve an entry by its column header than its position.