Dictionaries¶

• All of the compound data types we have studied in detail so far — strings, lists, and tuples — are sequential collections.
• This means that the items in the collection are ordered from left to right and they use integers as indices to access the values they contain.
• Dictionaries are a different kind of collection.
• They are Python’s built-in mapping type.
• A map is an unordered, associative collection.
• The association, or mapping, is from a key, which can be any immutable type, to a value, which can be any Python data object.

As an example, we will create a dictionary to translate English words into Spanish. For this dictionary, the keys are strings and the values will also be strings.

One way to create a dictionary is to start with the empty dictionary and add key-value pairs. The empty dictionary is denoted {}

Another way to create a dictionary is to provide a list of key-value pairs using the same syntax as the previous output.

It doesn’t matter what order we write the pairs. The values in a dictionary are accessed with keys, not with indices, so there is no need to care about ordering.

Here is how we use a key to look up the corresponding value.

The key 'two' yields the value 'dos'.