OOP model

Set up the class hierarchy and ABCs.

Function layer: count unique

In this lesson you will write the say function. This function counts unique words with set:

def say(words):
    return len(set(words))

print(say(words))  # 2

The starting code includes the previous lesson's solution. You will add the say function and its call. set(words) removes duplicates; len gives the unique count.

This is the fundamental way to summarise data.

Exercise Define and call the say function

Define def say(words): with return len(set(words)) in the body. Then write print(say(words)).

Show example solution

words = ["elma", "armut", "elma"]
print(len(words))
def say(words):
    return len(set(words))
print(say(words))

Next step: generator layer

The function layer is ready — you can count unique words. In the next lesson you will add a generator layer: producing words one by one with yield. This layer will save memory with large data.

Generators produce values without loading the whole list into memory; this makes them ideal for large files. Each lesson builds on top of the previous one and the starting code carries the previous solution.

Test yourself

Match the function layer

def say

Function
set(words)

Removes duplicates
len

Gives count
return

Returns a value
How many elements does set(["elma", "armut", "elma"]) have?
- 1
- 2
- 3
- 0
Show answer

2 — set removes duplicates; elma stays once, total 2.

Complete the say function

def say(words):
    return ____(set(words))

Show answer

def say(words):
    return len(set(words))

Next lesson: Generator layer

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