Creating dictionaries – inserting and updating

A dictionary is one kind of Python mapping. The built-in type dict class provides a number of common features. There are some common variations on these features defined in the collections module.

As we noted in the Choosing a data structure recipe, we'll use a dictionary when we have some key that we need to map to a given value. For example, we might want to map a single word to a long, complex definition of the word. Or perhaps some value to a count of the number of times that value has occurred in a dataset.

The key and count dictionary is very common. We'll look at a detailed recipe that shows how to initialize the dictionary and update the counter.

In the Using set methods and operators recipe we looked at the arrival of customers at a business. In that recipe, we used a set to determine how many visits were required before the business had collected a complete set of visits.

Getting ready

In this recipe, we'll look at creating a histogram...