CODEWITHSUNDEEP
pythonarrays
Julian Rubin
Julian Rubin

Reputation: 29

Joining two lists in Python:

I have two arrays (A & B). I would like to calculate the % of users of array A , who are included in array B. I have tried but I can´t find the solution.

Upvotes: 2

Views: 128

Answers (3)

Padraic Cunningham
Padraic Cunningham

Reputation: 180411

You only need to create one set and sum the times an element in a is in the set of the members in b:

st  = set(b)

perc = sum((ele in st for ele in a),0.0) / len(a) * 100

If you actually have numpy arrays:

import numpy as np

a, b = [1, 3], [1, 4,3]
perc = np.in1d(a, b).sum() / 100.0 / len(a)

Upvotes: 0

chris.stckhmr
chris.stckhmr

Reputation: 297

The most pyhtonic way is like Rogalski above commented.

Python in my opinion is very strong at sets: https://docs.python.org/2/library/sets.html

you can make an intersection in two ways

set(A) & set(B) or set(A).intersection(set(B))

And the formula is like mentioned above (just corrected)

100 * len(set(A) & set(B)) / len(set(A))

Upvotes: 4

Alex Hall
Alex Hall

Reputation: 36033

100.0 * sum((x in B) for x in A) / len(A)

If B is large, use a set for efficiency:

100.0 * len(set(B).intersection(A)) / len(A)

Upvotes: 9

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