CODEWITHSUNDEEP
pythonlistnested
Neuril
Neuril

Reputation: 183

Python nested lists join lookup reference list

New to python so apologies if this is trivial. I have a list

list = [3,1,0,2]

and a nested lookup

lookup = [[265,301,201],[225,302,191],[225,35,134],[28,82,158]]

I need to match every element in "list" with each corresponding element index in "lookup" and return the value of this element from "lookup". The result should be:

result = [
[28,82,158],
[225,302,191],
[265,301,201],
[225,35,134]
]

Upvotes: 3

Views: 126

Answers (3)

Padraic Cunningham
Padraic Cunningham

Reputation: 180391

A regular list comp and indexing:

lst = [3,1,0,2]

print([lookup[i] for i in lst])
[[28, 82, 158], [225, 302, 191], [265, 301, 201], [225, 35, 134]]

Or a functional approach using __getitem__:

lst = [3,1,0,2]


lookup = [[265,301,201],[225,302,191],[225,35,134],[28,82,158]]

print(list(map(lookup.__getitem__, lst)))

[[28, 82, 158], [225, 302, 191], [265, 301, 201], [225, 35, 134]]

using operator.itemgetter:

lst = [3,1,0,2]


lookup = [[265,301,201],[225,302,191],[225,35,134],[28,82,158]]
from operator import itemgetter

print(list(itemgetter(*lst)(lookup)))
 [[28, 82, 158], [225, 302, 191], [265, 301, 201], [225, 35, 134]]

Upvotes: 3

Hackaholic
Hackaholic

Reputation: 19733

you can use map and lambda too:

>>> lst = [3, 1, 0, 2]
>>> lookup = [[265,301,201],[225,302,191],[225,35,134],[28,82,158]]
>>> map(lambda x:lookup[x], lst)
[[28, 82, 158], [225, 302, 191], [265, 301, 201], [225, 35, 134]]

Upvotes: 1

Sven Marnach
Sven Marnach

Reputation: 601441

You can use a list comprehension:

result = [lookup[i] for i in list]

(Note that you shouldn't call a variable list. It will shadow the builtin of the same name, and will lead to unexpected beahaviour sooner or later.)

Upvotes: 3

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