cb8bbd9745
Update formatting in every_nth Update formatting in shuffle Update formatting in has_duplicates Update formatting in group_by Update formatting in sum_by Update formatting in zip Update formatting in longest_item Update formatting in bifurcate_by Update formatting in difference_by Update formatting in clamp_number Update formatting in min_by Update formatting in max_by Update formatting in union Update formatting in n_times_string Update formatting in check_prop Update formatting in chunk Update formatting in transpose Update formatting in bifurcate Update formatting in union_by Update formatting in initialize_list_with_range Update formatting in most_frequent
21 lines
667 B
Markdown
21 lines
667 B
Markdown
---
|
|
title: union_by
|
|
tags: list,function,intermediate
|
|
---
|
|
|
|
Returns every element that exists in any of the two lists once, after applying the provided function to each element of both.
|
|
|
|
Create a `set` by applying `fn` to each element in `a`, then use list comprehension in combination with `fn` on `b` to only keep values not contained in the previously created set, `_a`.
|
|
Finally, create a `set` from the previous result and `a` and transform it into a `list`
|
|
|
|
```py
|
|
def union_by(a, b, fn):
|
|
_a = set(map(fn, a))
|
|
return list(set(a + [item for item in b if fn(item) not in _a]))
|
|
```
|
|
|
|
```py
|
|
from math import floor
|
|
union_by([2.1], [1.2, 2.3], floor) # [2.1, 1.2]
|
|
```
|