From 2bcb06e48d5cf5d3033de4a674e25480bc688b42 Mon Sep 17 00:00:00 2001 From: Angelos Chalaris Date: Tue, 20 Aug 2019 15:16:27 +0300 Subject: [PATCH] Add intersection_by snippet --- snippets/intersection_by.md | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) create mode 100644 snippets/intersection_by.md diff --git a/snippets/intersection_by.md b/snippets/intersection_by.md new file mode 100644 index 000000000..2601c36ec --- /dev/null +++ b/snippets/intersection_by.md @@ -0,0 +1,19 @@ +--- +title: intersection_by +tags: list,function,intermediate +--- + +Returns a list of elements that exist in both lists, after applying the provided function to each list element of both. + +Create a `set` by applying `fn` to each element in `b`, then use list comprehension in combination with `fn` on `a` to only keep values contained in both lists. + +```py +def intersection_by(a, b, fn): + _b = set(map(fn, b)) + return [item for item in a if fn(item) in _b] +``` + +```py +from math import floor +intersection_by([2.1, 1.2], [2.3, 3.4],floor) # [2.1] +``` \ No newline at end of file