CODEWITHSUNDEEP
python
Bob McBobson
Bob McBobson

Reputation: 914

How to make sure that my list comprehension returns a list of strings that are not present in a different list?

I want to make a list comprehension that iterates through a list of strings, and only gives me back strings which are not present in another predefined list.

samples= ['abc', 'cab', 'bth', 'doc', 'bue']
unwanted= ['doc', 'bue']
wanted_samples= [sample for sample in samples if sample #checks if sample is present in unwanted list]

I have tried to set this up in a couple ways, but it has not worked yet. Any help would be great. It seems like something I should have figured out a while ago, but my brain has just not been cooperating with me today.

Upvotes: 0

Views: 33

Answers (3)

Jaime Ortiz
Jaime Ortiz

Reputation: 1319

You can achieve that by doing this

wanted_samples = [sample for sample in samples if sample not in unwanted]

if the sample is present in the unwanted list, the sample will not be added to wanted_samples

Upvotes: 1

Siddharth Gawande
Siddharth Gawande

Reputation: 21

You can use not in operator wanted_samples = [sample for sample in samples if sample not in unwanted]

Upvotes: 1

S.B
S.B

Reputation: 16526

use not in:

wanted_samples = [sample for sample in samples if sample not in unwanted]

if it's a sample and your unwanted list has a lot of words, I suggest using set instead(unwanted= {'doc', 'bue', ...}). Time Complexity of membership testing for set is O(1).

Upvotes: 1

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