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diff --git a/blog/python_list_comprehension.md b/blog/python_list_comprehension.md new file mode 100644 index 0000000..73cd116 --- /dev/null +++ b/blog/python_list_comprehension.md @@ -0,0 +1,87 @@ +# Python's list comprehension + +List comprehension are the best feature of Python. They allow us to map and filter the elements of lists. + +## Mapping + +You can change each element of a list. + +``` +>>> xs = [x * x for x in range(10)] +>>> xs +[0, 1, 4, 9, 16, 25, 36, 49, 64, 81] +>>> [x + 10 for x in xs] +[10, 11, 14, 19, 26, 35, 46, 59, 74, 91] +``` + +### Syntax + +``` +[<expr> for <element> in <iterable>] +``` + +The result of `<expr>` will be the value of the element. + +### Comparison + +``` +result = [] +for <element> in <iterable>: + result.append(<expr>) +``` + +## Filter + +You can filter out elements. + +``` +>>> [x for x in range(10) if x % 2 == 0] +[0, 2, 4, 6, 8] +>>> [x * x for x in range(10) if x > 5] +[36, 49, 64, 81] +``` + +### Syntax + +``` +[<expr> for <element> in <iterable> if <condition>] +``` + +The result of `<expr>` will be the value of the element if `<condition>` is `True`. + +### Comparison + +``` +result = [] +for <element> in <iterable>: + if <condition>: + result.append(<expr>) +``` + +## Other comprehension + +### Dictionnary + +``` +>>> {k: v * v for k, v in {"foo": 1, "bar": 2}.items()} +{"foo": 1, "bar": 4} +``` + +### Set + +``` +>>> {x for x in [1, 2, 3, 1, 1, 1, 2, 1]} +{1, 2, 3} +``` + +### Generator + +``` +>>> gen = (x * x for x in range(10)) +>>> next(gen) +0 +>>> next(gen) +1 +>>> next(gen) +4 +``` |
