filter() function in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to filter out even numbers from the list.

Python

numbers = [1, 2, 3, 4, 5]
even_numbers = list(filter([1], numbers))
print(even_numbers)

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Alambda x: x % 2 == 0

Blambda x: x * 2

Clambda x: x + 2

Dlambda x: x - 2

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function that changes the number instead of returning True/False.

Forgetting to convert the filter object to a list.

The filter() function needs a function that returns True for even numbers. lambda x: x % 2 == 0 does exactly that.

2fill in blank

medium

Complete the code to filter words longer than 3 characters.

Python

words = ['cat', 'lion', 'dog', 'elephant']
long_words = list(filter([1], words))
print(long_words)

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Alambda w: w.startswith('e')

Blambda w: len(w) > 3

Clambda w: w == 'dog'

Dlambda w: len(w) < 3

Attempts:

3 left

💡 Hint

Common Mistakes

Using < 3 instead of > 3.

Filtering by exact word instead of length.

The filter function should keep words with length greater than 3, so lambda w: len(w) > 3 is correct.

3fill in blank

hard

Fix the error in the filter function to keep only positive numbers.

Python

numbers = [-2, 0, 3, 5, -1]
positive = list(filter([1], numbers))
print(positive)

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Alambda x: x != 0

Blambda x: x >= 0

Clambda x: x < 0

Dlambda x: x > 0

Attempts:

3 left

💡 Hint

Common Mistakes

Including zero as positive by using >= instead of >.

Filtering negative numbers instead of positive.

To keep only positive numbers (greater than zero), use lambda x: x > 0. Using x >= 0 would include zero, which is not positive.

4fill in blank

hard

Fill both blanks to filter words starting with 'a' and convert them to uppercase.

Python

words = ['apple', 'banana', 'avocado', 'cherry']
filtered = list(filter([1], words))
result = [w.[2]() for w in filtered]
print(result)

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Alambda w: w.startswith('a')

Blambda w: w.endswith('a')

Cupper

Dlower

Attempts:

3 left

💡 Hint

Common Mistakes

Using endswith instead of startswith.

Using lower() instead of upper().

The filter keeps words starting with 'a' using lambda w: w.startswith('a'). Then, upper() converts them to uppercase.

5fill in blank

hard

Fill all three blanks to filter numbers divisible by 3, square them, and keep only those greater than 10.

Python

numbers = [1, 3, 4, 6, 9, 12]
filtered = filter([1], numbers)
squared = map(lambda x: x[2]2, filtered)
result = list(filter(lambda x: x [3] 10, squared))
print(result)

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Alambda x: x % 3 == 0

B**

C>

Dlambda x: x % 2 == 0

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong lambda for filtering divisible numbers.

Using multiplication instead of exponentiation for squaring.

Using < instead of > in the last filter.

First, filter numbers divisible by 3 with lambda x: x % 3 == 0. Then square them using ** 2. Finally, keep only squares greater than 10 with > 10.