Chapter 8 Exercises

Comprehensive exercises covering iterators and generators in Python.

By Ali Berro

January 9, 2026 12 min read Section

From: Python Fundamentals: From Zero to Hero

python iterators generators yield

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Section 55 of 61

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Chapter 8 Exercises

Comprehensive exercises covering iterators and generators in Python, sorted from easiest to hardest.

Exercises

Exercise 1: Basic Iterator Class

Create a class called CountDown that implements the iterator protocol. It should start at a given number and count down to 0 (inclusive). Read the start value and print all numbers.

Answer:

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class CountDown:
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    def __init__(self, start):
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        self.current = start
4

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    def __iter__(self):
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        return self
7

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    def __next__(self):
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        if self.current < 0:
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            raise StopIteration
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        value = self.current
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        self.current -= 1
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        return value
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start = int(input())
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counter = CountDown(start)
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for num in counter:
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    print(num)

Exercise 2: Basic Generator Function

Create a generator function called squares that takes a limit n and yields squares of numbers from 0 to n-1. Read n and print all squares.

Answer:

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def squares(limit):
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    for i in range(limit):
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        yield i ** 2
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n = int(input())
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for square in squares(n):
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    print(square)

Exercise 3: Using iter() and next()

Create a list [10, 20, 30, 40, 50]. Use iter() to get an iterator, then use next() to get the first three values. Print each value on a separate line.

Answer:

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my_list = [10, 20, 30, 40, 50]
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iterator = iter(my_list)
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print(next(iterator))
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print(next(iterator))
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print(next(iterator))

Exercise 4: Generator Expression

Create a generator expression that generates cubes (x³) of numbers from 0 to n-1. Read n, convert to list, and print.

Answer:

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n = int(input())
2
cubes = (x ** 3 for x in range(n))
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print(list(cubes))

Exercise 5: Using enumerate()

Read a number n, then read n strings. Use enumerate() to iterate and print each string with its 1-based index in format “Index: value”.

Answer:

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n = int(input())
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items = []
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for i in range(n):
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    items.append(input())
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for index, value in enumerate(items, start=1):
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    print(f"{index}: {value}")

Exercise 6: Using zip()

Read two numbers n and m, then read n names and m scores. Use zip() to combine them and print each name with its score in format “Name: Score”. If lists differ in length, process only the shorter length.

Answer:

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n = int(input())
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m = int(input())
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names = []
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for i in range(n):
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    names.append(input())
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scores = []
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for i in range(m):
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    scores.append(int(input()))
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for name, score in zip(names, scores):
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    print(f"{name}: {score}")

Exercise 7: Even Numbers Generator

Create a generator function even_numbers that takes start and end, and yields even numbers in that range (inclusive start, exclusive end). Read start and end, print all even numbers.

Answer:

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def even_numbers(start, end):
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    for num in range(start, end):
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        if num % 2 == 0:
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            yield num
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start = int(input())
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end = int(input())
8

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for num in even_numbers(start, end):
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    print(num)

Exercise 8: Custom Range Iterator

Create a class MyRange implementing the iterator protocol. It takes start, stop, and optional step (default 1), and yields values like range(). Read start, stop, step, then print all values.

Answer:

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class MyRange:
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    def __init__(self, start, stop, step=1):
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        self.start = start
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        self.stop = stop
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        self.step = step
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        self.current = start
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    def __iter__(self):
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        return self
10

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    def __next__(self):
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        if (self.step > 0 and self.current >= self.stop) or \
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           (self.step < 0 and self.current <= self.stop):
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            raise StopIteration
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        value = self.current
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        self.current += self.step
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        return value
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start = int(input())
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stop = int(input())
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step = int(input())
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my_range = MyRange(start, stop, step)
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for num in my_range:
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    print(num)

Exercise 9: Fibonacci Generator

Create a generator function fibonacci that takes a limit and yields the first limit Fibonacci numbers. Read limit and print all numbers.

Answer:

1
def fibonacci(limit):
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    prev, curr = 0, 1
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    count = 0
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    while count < limit:
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        yield prev
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        prev, curr = curr, prev + curr
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        count += 1
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limit = int(input())
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for num in fibonacci(limit):
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    print(num)

Exercise 10: Generator with Condition

Create a generator expression that generates numbers from 0 to n-1 divisible by 3 or 5. Read n, convert to list, and print.

Answer:

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n = int(input())
2
divisible = (x for x in range(n) if x % 3 == 0 or x % 5 == 0)
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print(list(divisible))

Exercise 11: Using reversed()

Read a number n, then read n integers into a list. Use reversed() to iterate in reverse order and print each number.

Answer:

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n = int(input())
2
numbers = []
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for i in range(n):
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    numbers.append(int(input()))
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for num in reversed(numbers):
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    print(num)

Exercise 12: Prime Numbers Generator

Create a generator function primes that takes a limit and yields all prime numbers up to (but not including) limit. Read limit and print all primes.

Answer:

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def is_prime(n):
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    if n < 2:
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        return False
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    for i in range(2, int(n ** 0.5) + 1):
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        if n % i == 0:
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            return False
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    return True
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def primes(limit):
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    for num in range(2, limit):
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        if is_prime(num):
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            yield num
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limit = int(input())
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for prime in primes(limit):
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    print(prime)

Exercise 13: Iterator with State

Create a class Cycle that implements the iterator protocol. It takes a list and cycles through it indefinitely (or up to a limit). Read n (number of items), then the items, then limit. Print limit values from the cycle.

Answer:

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class Cycle:
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    def __init__(self, items, limit):
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        self.items = items
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        self.limit = limit
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        self.index = 0
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        self.count = 0
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    def __iter__(self):
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        return self
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    def __next__(self):
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        if self.count >= self.limit:
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            raise StopIteration
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        value = self.items[self.index]
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        self.index = (self.index + 1) % len(self.items)
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        self.count += 1
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        return value
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n = int(input())
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items = []
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for i in range(n):
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    items.append(input())
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limit = int(input())
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cycle = Cycle(items, limit)
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for item in cycle:
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    print(item)

Exercise 14: Generator Pipeline

Create two generator functions: numbers(n) that yields 0 to n-1, and squares(nums) that takes an iterator and yields squares. Chain them: squares(numbers(n)). Read n and print all squared values.

Answer:

1
def numbers(n):
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    for i in range(n):
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        yield i
4

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def squares(nums):
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    for num in nums:
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        yield num ** 2
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n = int(input())
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pipeline = squares(numbers(n))
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for value in pipeline:
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    print(value)

Exercise 15: Multiple Generator Expressions

Create a generator expression that generates pairs (x, y) where x and y are from 0 to n-1, but only include pairs where x < y. Read n, convert to list, and print.

Answer:

1
n = int(input())
2
pairs = ((x, y) for x in range(n) for y in range(n) if x < y)
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print(list(pairs))

Exercise 16: Separating Iterable and Iterator

Create a class Squares (iterable) that has __iter__() returning a SquareIterator. SquareIterator yields squares from 0 to n-1. Read n, create Squares, iterate twice to show independent iterations.

Answer:

1
class SquareIterator:
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    def __init__(self, limit):
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        self.current = 0
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        self.limit = limit
5

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    def __iter__(self):
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        return self
8

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    def __next__(self):
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        if self.current >= self.limit:
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            raise StopIteration
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        value = self.current ** 2
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        self.current += 1
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        return value
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class Squares:
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    def __init__(self, limit):
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        self.limit = limit
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    def __iter__(self):
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        return SquareIterator(self.limit)
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n = int(input())
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squares = Squares(n)
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for num in squares:
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    print(num)
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for num in squares:
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    print(num)

Exercise 17: Infinite Generator

Create an infinite generator function natural_numbers() that yields natural numbers starting from 1. Use it to print the first n natural numbers. Read n.

Answer:

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def natural_numbers():
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    num = 1
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    while True:
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        yield num
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        num += 1
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n = int(input())
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gen = natural_numbers()
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for i in range(n):
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    print(next(gen))

Exercise 18: Complex Generator Function

Create a generator function multiples_of(m, limit) that yields multiples of m up to limit. Read m and limit, print all multiples.

Answer:

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def multiples_of(m, limit):
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    num = m
3
    while num < limit:
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        yield num
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        num += m
6

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m = int(input())
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limit = int(input())
9

10
for multiple in multiples_of(m, limit):
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    print(multiple)

Exercise 19: Generator with Multiple Yields

Create a generator function alternating_pattern(n) that yields “even”, “odd”, “even”, “odd” for n iterations. Read n and print all values.

Answer:

1
def alternating_pattern(n):
2
    for i in range(n):
3
        if i % 2 == 0:
4
            yield "even"
5
        else:
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            yield "odd"
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n = int(input())
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for value in alternating_pattern(n):
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    print(value)

Exercise 20: Complete Iterator System

Create a class BoundedRange implementing the iterator protocol. It takes start, stop, step, and max_iterations. It yields values like range but stops after max_iterations. Read all parameters and print values.

Answer:

1
class BoundedRange:
2
    def __init__(self, start, stop, step, max_iterations):
3
        self.start = start
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        self.stop = stop
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        self.step = step
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        self.current = start
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        self.max_iterations = max_iterations
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        self.count = 0
9

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    def __iter__(self):
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        return self
12

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    def __next__(self):
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        if self.count >= self.max_iterations:
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            raise StopIteration
16

17
        if (self.step > 0 and self.current >= self.stop) or \
18
           (self.step < 0 and self.current <= self.stop):
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            raise StopIteration
20

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        value = self.current
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        self.current += self.step
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        self.count += 1
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        return value
25

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start = int(input())
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stop = int(input())
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step = int(input())
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max_iter = int(input())
30

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bounded = BoundedRange(start, stop, step, max_iter)
32
for num in bounded:
33
    print(num)

Course Progress

Section 55 of 61

Back to Course

Table of Contents

Table of Contents

Course Progress

Chapter 8 Exercises

Exercises

Exercise 1: Basic Iterator Class

Exercise 2: Basic Generator Function

Exercise 3: Using iter() and next()

Exercise 4: Generator Expression

Exercise 5: Using enumerate()

Exercise 6: Using zip()

Exercise 7: Even Numbers Generator

Exercise 8: Custom Range Iterator

Exercise 9: Fibonacci Generator

Exercise 10: Generator with Condition

Exercise 11: Using reversed()

Exercise 12: Prime Numbers Generator

Exercise 13: Iterator with State

Exercise 14: Generator Pipeline

Exercise 15: Multiple Generator Expressions

Exercise 16: Separating Iterable and Iterator

Exercise 17: Infinite Generator

Exercise 18: Complex Generator Function

Exercise 19: Generator with Multiple Yields

Exercise 20: Complete Iterator System

Course Progress