list comprehension vs. lambda + filter?

Question

I happened to find myself having a basic filtering need: I have a list and I have to filter it by an attribute of the items.My code looked like this: my_list = [x for x in my_list if x.attribute == value]But then I thought, wouldn't it be better to write it like this? my_list = filter(lambda x: x.attribute == value, my_list)It's more readable, and if needed for performance the lambda could be taken out to gain something. Question is: are there any caveats in using the second way? Any performance difference? Am I missing the Pythonic Way™ entirely and should do it in yet another way (such as using itemgetter instead of the lambda)?

Answer 1

The list comprehension is less noisy especially when nesting anonymous functions and also allows for filtering natively whereas map would require the filter function to achieve the same effect.

Example from Effective Python by Brett Slatkin:

even_squares = [x ** 2 for x in range(1, 11) if x % 2 == 0]

print(even_squares)

# [4, 16, 36, 64, 100]

even_squares2 = list(map(lambda x: x ** 2, filter(lambda x: x % 2 == 0, range(1, 11))))

print(even_squares2)

# [4, 16, 36, 64, 100]

Another reason is that dictionaries and sets in Python also have equivalent comprehension statements that can't really be generated with map and filter.