Searching and counting elements in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Counting occurrences in a list

What is the output of this code that counts how many times the number 3 appears in the list?

Python

numbers = [1, 3, 5, 3, 7, 3, 9]
count_3 = numbers.count(3)
print(count_3)

A 4

B 2

C 3

D 1

💡 Hint

Use the list method that counts how many times an item appears.

The list method count(x) returns how many times x appears in the list. Here, 3 appears three times.

❓ Predict Output

intermediate

Finding the index of an element

What will be printed by this code that finds the first position of the string 'apple' in the list?

Python

fruits = ['banana', 'apple', 'orange', 'apple']
index = fruits.index('apple')
print(index)

A 0

B 1

C 3

D 2

💡 Hint

The index method returns the first position where the item is found.

The first 'apple' is at position 1 (counting from zero).

❓ Predict Output

advanced

Counting elements with a condition

What is the output of this code that counts how many numbers in the list are greater than 5?

Python

nums = [2, 7, 4, 9, 5, 8]
count = sum(1 for n in nums if n > 5)
print(count)

A 3

B 4

C 2

D 5

💡 Hint

Sum 1 for each number that meets the condition n > 5.

Numbers greater than 5 are 7, 9, and 8, so count is 3.

❓ Predict Output

advanced

Finding the first matching element with next()

What will this code print? It finds the first even number in the list or returns -1 if none found.

Python

numbers = [1, 3, 5, 8, 10]
first_even = next((x for x in numbers if x % 2 == 0), -1)
print(first_even)

A 8

B 10

C -1

D 5

💡 Hint

next() returns the first item from the generator that meets the condition.

The first even number is 8, so it prints 8.

❓ Predict Output

expert

Counting unique elements with a condition

What is the output of this code that counts how many unique words in the list have length greater than 3?

Python

words = ['cat', 'dog', 'elephant', 'dog', 'bird', 'cat', 'elephant']
unique_words = set(words)
count = sum(1 for w in unique_words if len(w) > 3)
print(count)

A 1

B 3

C 4

D 2

💡 Hint

Convert list to set to get unique words, then count those longer than 3 letters.

Unique words are {'cat', 'dog', 'elephant', 'bird'}. Only 'elephant' and 'bird' have length > 3, so count is 2.