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Python Data Structures in Practice

Recap
2. Recap
Using sets to compute unique elements
Set operations
Simulating machines
Summary

Instruction

Before we dive into the actual applications of sets, let's do a quick review.

set

As you may remember, sets are unordered collections of elements – there is no "first" or "last" element. Also, sets can only store unique elements; duplicates are not allowed.

Let's take a look at some basic set operations:

  1. Define a set:
    2. empty_set = set()
letters = {'a', 'd', 'f', 'h'}
  2. Add an element:
    3. letters.add('t')
  3. Remove one element:
    4. letters.discard('d')
  4. Remove all elements:
    5. letters.clear()
  5. Iterate over a set:
    6. for letter in letters:
  ...
  6. Check if an element is in a set:
    7. if letter in letters:
  ...

How about a quick warmup exercise?

Exercise

Write a function named count_unique_letters(word) that accepts a string argument and returns the number of unique letters (characters) in the word.

Stuck? Here's a hint!

Within a loop, add each letter of the string to a set. Then, return the length of the set with:

len(unique_letters)