Effective Python memo Item 7 Use list comprehension instead of map and filter

Notes on Effective Python

Item 5: Use list comprehension instead of map and filter (p15 ~ 16)

In most cases, comprehensions are cleaner and easier to read than using higher-order functions

Higher-order functions are functional and cool (?), But they generate lambdas one by one, so it's difficult to read unless you're used to it. Guido seems to dislike higher-order functions in the first place, and there will be a limited number of situations where he will actively use them.

If you can use the inclusion notation, write it in the inclusion notation!

Example of squaring a sequence

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

#Write an expression that squares each sequence

# map()in the case of
squares = map(lambda x: x ** 2, a)
print(list(squares))

>>>
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

#In case of inclusion notation
squares = [x ** 2 for x in a]
print(squares)

>>>
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

The latter is easier to see, isn't it? Let's add a condition to extract only even numbers.

#Only even numbers are squared and extracted

# map()And filter()If you write in
even_squares = map(lambda x: x**2, filter(lambda x: x % 2 == 0, a))
print(list(even_squares))

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

#In case of inclusion notation
even_squares = [x **2 for x in a if x % 2 == 0]
print(even_squares)

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

This is clearer! There is no room for hesitation

By the way, not only lists but also dictionaries and sets can be used for inclusion notation.

#Invert dictionary keys and values, create new dictionaries
chile_ranks = {'ghost': 1, 'habanero': 2, 'cayenne': 3}
rank_dist = {rank: name for name, rank in chile_ranks.items()}
chile_len_set = {len(name) for name in rank_dist.values()}
print(rank_dist)
print(chile_len_set)

>>>
{1: 'ghost', 2: 'habanero', 3: 'cayenne'}
{8, 5, 7}

Summary

Higher-order functions aren't bad, but it's better to write your code for readability. (Except for those who really like functional programming ...)