CODEWITHSUNDEEP
pythonlist
user11735387
user11735387

Reputation:

How would I find the intersection of two lists in python without using sets

I have a program with two very large lists, one with 3^12 terms and the other with 5000 terms, and I want to find the intersection of them (items that are the same in both lists).

I have already tried using sets and loops(see below).

I have tried (in Python 3)

[i for i in joinedCombs if i in dictionary]

and

endResult = list(set(joinedCombs)&set(dictionary))

I get a time error for the first line of code and a memory error for the second line of code. What could I do to balance out speed and time? Please leave an answer, not a comment

Upvotes: 0

Views: 140

Answers (2)

chepner
chepner

Reputation: 532448

Use len to determine which list is the shorter one, and create a set from that:

[i for i in joinedCombs if i in dictionary]
if len(joinedCombs) < len(dictionary):
    s1 = set(dictionary)
    itr = joinedCombs
else:
    s1 = set(joinedCombs)
    itr = dictionary

new = [i for i in itr if i in s1]

Upvotes: 1

F Blanchet
F Blanchet

Reputation: 1510

You can try this line of code :

endResult = list(set(joinedCombs).intersection(dictionary))

Upvotes: 0

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