How do I use map and filter in Python?

How do I use map and filter in Python?

In Python, map() applies a function to all items in an iterable, while filter() filters items based on a condition.

Can you give me an example of using both functions?

Sure! Here's an example:

# Using map to square numbers
numbers = [1, 2, 3, 4]
squared = list(map(lambda x: x**2, numbers))

# Using filter to get even numbers
even_numbers = list(filter(lambda x: x % 2 == 0, numbers))

This will give you squared as [1, 4, 9, 16] and even_numbers as [2, 4].

What if I want to combine both map and filter?

You can combine them by first filtering the list and then mapping the result. For example:

filtered_squared = list(map(lambda x: x**2, filter(lambda x: x % 2 == 0, numbers)))

This will give you the squares of the even numbers.

Thanks! Are there any performance considerations when using these functions?

Yes, using map() and filter() can be more memory efficient than list comprehensions, especially with large datasets, as they return iterators.