Python List/Dict Comprehension

Something like this

new_list = [expression for member in iterable if conditional]

Dict comprehension:

>>> quote = "life, uh, finds a way"
>>> {char for char in quote if char in "aeiou"}
{'a', 'e', 'u', 'i'}

Nesting

List comprehension can be used to perform “nested loops.” The syntax loops like the following:

new_list = [expression(item) for inner_iterable in outer_iterable for item in inner_iterable]

The above code is equivalent to

new_list = []
for inner_iterable in outer_iterable:
    for item in inner_iterable:
        new_list.append(expression(item))

For example, we can use List comprehension to flatten a nested list:

nested = [[1, 2, 3], [4, 5], [6, 7, 8, 9]]
[item for inner in nested for item in inner]
# Output: [1, 2, 3, 4, 5, 6, 7, 8, 9]

pairs = [(item1, item2) for item1 in list1 for item2 in list2]