List Comprehension
When we want to filter out values from an exiting list we place the if block towards the end of the comprehension
sentence = 'the rocket came back from mars'
vowels = [i for i in sentence if i in 'aeiou']
# ['e', 'o', 'e', 'a', 'e', 'a', 'o', 'a']When we have to use the else condition in the comprehension we have to use the ternary operator syntax which places the condition before the for loop
original_prices = [1.25, -9.45, 10.22, 3.78, -5.92, 1.16]
prices = [i if i > 0 else 0 for i in original_prices]
# [1.25, 0, 10.22, 3.78, 0, 1.16]Set and Dictionary Comprehension
- If we replace the
[]in list comprehension with{}we get set comprehension. Set comprehension does not guarantee the order of elements - Dictionary comprehension is similar to set comprehension with the additional requirement of having to pass a key-value pair
quote = "life, uh, finds a way"
unique_vowels = {i for i in quote if i in 'aeiou'}
# {'a', 'e', 'u', 'i'}
squares = {i: i * i for i in range(10)}
# {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}