list, set, and dict comprehensions
The Python list, set, and dict comprehensions are a very easy way to apply a function or filter to a list of items.
When used correctly, list/set/dict comprehensions can be really useful for quick filtering or transforming of lists, sets, and dicts. The same results can be achieved using the “functional” functions map and filter, but list/set/dict comprehensions are often easier to use and also easier to read.
Basic list comprehensions
Let’s dive right into a few examples. The basic premise of a list comprehension looks like this:
>>> squares = [x ** 2 for x in range(10)]
>>> squares
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
We can easily expand this with a filter:
>>> odd_squares = [x ** 2 for x in range(10) if x % 2]
>>> odd_squares
[1, 9, 25, 49, 81]
This brings us to the version that is common in most functional languages using map and filter:
>>>...
