List Comprehensions

Another awesome python feature is List Comprehension. It is basically a one liner for loop built inside brackets

lst = [x for x in range(10)]

print(lst)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

You can even run mathematical functions inside list comprehension

lst = [x**2 for x in range(10)]

print(lst)
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

Making a list out of any word

lst = [x for x in 'hello']

print(lst)
['h', 'e', 'l', 'l', 'o']

List comprehension with only ‘If’ statement

lst = [x for x in range(10) if x%2==0]

print(lst)
[0, 2, 4, 6, 8]

List comprehension with ‘If-else’ statement

lst = [x if x%2==0 else 'odd' for x in range(10)]

print(lst)
[0, 'odd', 2, 'odd', 4, 'odd', 6, 'odd', 8, 'odd']

Nested list comprehensions

lst = [x*2 for x in [x*2 for x in range(5)]]

print(lst)
[0, 4, 8, 12, 16]

Nested for loops inside list comprehensions

[(x,y) for x in range(3) for y in range(3)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]

for x in range(3):
    for y in range(3):
        print(f'({x},{y})',end=', ')
(0,0), (0,1), (0,2), (1,0), (1,1), (1,2), (2,0), (2,1), (2,2)