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Recap
Using sets to compute unique elements
5. Creating sets with unique element characteristics
Set operations
Simulating machines
Summary

## Instruction

Perfect! We can also use sets to store the unique values of a characteristic computed from the elements of a given list. Take a look:

cities = ['London', 'Madrid', 'Milan', 'Bordeaux', 'Milan', 'London', 'Lisbon', 'London']
first_letters = set()
for city in cities:
first_letters.add(city[0])

In the example above, we want to find all the unique first letters for the elements in the list. Inside a loop, we simply add the first letter of each city to the first_letters set. Because sets only hold unique values, duplicates will be ignored when we invoke first_letters.add(city[0]).

## Exercise

We want to manufacture key rings with the car makes found in the people_cars dictionary. The size of each key ring will depend on the number of letters in the car make name. Create the set named car_make_lengths and add all unique car make length values to it. Then, print the following sentence:

There will be {x} different sizes of key rings.

### Stuck? Here's a hint!

Iterate over all the values in the dictionary with people_cars.values() and add len(value) to your set.

To get the size of the set, use the len() function.