A dictionary is a collection of items.

Each item in the collection has a key and a value

We use the key to set and get the value.

First we create a dictionary with the keys and values. This example will be a dictionary of names to ages

ages = {
  'bob': 54,
  'alice': 36,
  'carl': 21 
}

In the example you can see each name is a key, and the key is a type string. The key has a value specified with the colon symbol :

So the format is 'key': value. We use a comma to seperate the items.

To get a value from a dictionary, we use the name of the dictionary and the key

ages = {
  'bob': 54,
  'alice': 36,
  'carl': 21 
}

value = ages['alice']
print(value)

value = ages['carl']
print(value)

We can also change the value for a key in a dictionary using the assignment operator =

Why do we want a dictionary?

Since we can use the key to get and set a value, we only need one variable to do this, the name of the dictionary. Otherwise we would need a variable for each key. A dictionary can store thousands of keys, which is much better than thousands of variables. Also, variable names are set in code and can't change. With a dictionary, you can add a new item and value using the assingment operator.

A disctionary is an easy way to store values while the program is running and you don't know how many values you will need.