Using map() and filter()

Have you ever wanted to transform or filter a list without writing a for loop?
Python gives you two functional tools: map() to apply a function, and filter() to select items by condition.

Using map()

nums = [1, 2, 3, 4]
doubled = list(map(lambda x: x * 2, nums))
print(doubled)

# [2, 4, 6, 8]

Using filter()

nums = [1, 2, 3, 4, 5]
evens = list(filter(lambda x: x % 2 == 0, nums))
print(evens)

# [2, 4]

Equivalent with list comprehensions

nums = [1, 2, 3, 4, 5]
doubled = [x * 2 for x in nums]
evens = [x for x in nums if x % 2 == 0]
print(doubled)
print(evens)

# [2, 4, 6, 8, 10]
# [2, 4]

Conclusion

• map() transforms items.
• filter() keeps items matching a condition.
• List comprehensions often make code more Pythonic, but map() and filter() remain powerful tools.