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Comments on How do I trim a sorted list in Python?

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How do I trim a sorted list in Python?

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How do I trim a sorted list in Python, so that I only keep the elements greater than a certain value?

For example, if I have this list:

l = [1, 3, 5, 6, 7, 8]

How can I efficiently get a list of numbers greater than 4?

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The library module itertools provides a function called dropwhile().

The example they give is:

dropwhile(lambda x: x<5, [1,4,6,3,8]) 
→ 6 3 8

So, to get a list of numbers greater than 4, drop items while they are less than or equal to 4:

import itertools

l = [1, 3, 5, 6, 7, 8]
result = itertools.dropwhile(lambda x: x<=4, l)

Note that result at this point will be a lazy iterator object of some kind, not an actual list. So you might have to do: print(*result) to confirm it works. But you can iterate it, or call list(result) to make it a true list. (Remember, also, that iterators get consumed.)

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Not the most efficient solution (1 comment)
Not the most efficient solution
mr Tsjolder‭ wrote 6 months ago

Although Python is not necessarily an efficiency-oriented language, it might be useful to point out that this approach is probably not as efficient as a bisection algorithm.