How to get an index of an item within a range in python list?

Question

(Re-edited) For example, I have a list-like array:

l = [0.3, 2.3, 3.1, 4.5] # value can be any numeric type

Then given a number 1.2, as it is between 0.3 and 2.3, index 1 should be returned, and given a number 3.3, which is between 3.1 and 4.5, index 3 should be returned, for value less than 0.3, should return index 0, etc.

Basically for whatever input value, depends on the bin it falls into, return the index of that bin.

I hope not use if else statement, as the number of items in the list could be huge.

I guess the question should have been asked somewhere, but I just can't locate it.

(BTW, I actually remember there is a built-in function in numpy does the trick, but I can't recall anymore ...)

Is the rounding strategy toward zero like in `round(n)` or toward negative infinity like in floor division `n // 1`? — wjandrea, Sep 21 '19 at 19:50
Maybe you're looking for this? [binning data in python with scipy/numpy](https://stackoverflow.com/q/6163334/4518341) — wjandrea, Sep 21 '19 at 19:57
@wjandrea Exactly `np.digitize` is what I am looking for, thanks for the quick response! I used this function before, but forgot that... — MJeremy, Sep 21 '19 at 20:13

score 1 · Answer 1 · answered Sep 21 '19 at 19:36

1

>>> l.index(round(1.2))
0
>>> l.index(round(3.3))
2

Assuming normal rounding rules.

answered Sep 21 '19 at 19:36

Snorre Løvås

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I am looking for more general case, the values in the list does not have to be `int` – MJeremy Sep 21 '19 at 19:47

score 0 · Answer 2 · edited Sep 21 '19 at 19:47

0

The floor function from math library can also be used.

>>> l.index(floor(1.2))
0

edited Sep 21 '19 at 19:47

wjandrea

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answered Sep 21 '19 at 19:42

Anirudh Maheswaram

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score 0 · Answer 3 · edited Sep 21 '19 at 19:52

0

Other answers assumed that we have order step 1 array. in general form you can use something like this:

# for 1.5
l.index(max(x for x in l if x < 1.5))
# output: 0
# for 2.5
l.index(max(x for x in l if x < 2.5))
# output: 1

Caution: I assumed that there is no repeat in data and it sorted

edited Sep 21 '19 at 19:52

wjandrea

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answered Sep 21 '19 at 19:45

SirSaleh

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How to get an index of an item within a range in python list?

3 Answers3