CODEWITHSUNDEEP
python
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W H Help

Reputation: 105

Need to check if value is between two numbers in a list

I have a list in my python script [79.99, 82.99, 83.99, 84.99, 85.99, 86.99, 87.99, 88.99, 89.99] and an ever increasing number in a loop. I want to create a condition so when this number reaches a number between one of those ranges, it will take the lower number of the range and process it.

For example while (i!=10000): i=+1 and if i between range(above_range): print(low_Range_number)

if the number would be 81.99, it would pick 79.99 if the number would be 84.23, it would pick 83.99

Upvotes: 0

Views: 7146

Answers (3)

Adam Smith
Adam Smith

Reputation: 54203

This is what the bisect stdlib module is made for.

import bisect

entries = [79.99, 82.99, 83.99, 84.99, 85.99, 86.99, 87.99, 88.99, 89.99]
x = 81.5

def get_lower_bound(haystack, needle):
    """Get lower bound between two numbers in a sorted list

    If needle is lower than the lower bound, or higher than the higher bound of
    the sorted list, then raise ValueError.

    >>> get_lower_bound([1,2,3], 1.5)
    1
    >>> get_lower_bound([1,2,3], 2)
    2
    >>> get_lower_bound([1,2,3], 0)
    Traceback (most recent call last):
    ...
    ValueError: 0 is out of bounds of [1, 2, 3]
    >>> get_lower_bound([1,2,3], 4)
    Traceback (most recent call last):
    ...
    ValueError: 4 is out of bounds of [1, 2, 3]
    """

    idx = bisect.bisect(haystack, needle)
    if 0 < idx < len(haystack):
        return haystack[idx-1]
    else:
        raise ValueError(f"{needle} is out of bounds of {haystack}")

Upvotes: 8

Esteban Salpeter
Esteban Salpeter

Reputation: 41

You add your value to the list, sort it, find your value's index and then ask for the previous one (finally remove your value):

a = [79.99, 82.99, 83.99, 84.99, 85.99, 86.99, 87.99, 88.99, 89.99]
limit = len(a)
for i in range(0, 10000):
    a.append(i)
    a.sort()
    ix = a.index(i)
    if ix > 0 and ix <= limit: print(a[ix-1])
    a.remove(i)

Upvotes: 2

knh190
knh190

Reputation: 2882

Your list seems to be sorted, so:

def lower_bound(x, l):
    if not l or l[0] > x:
        return
    for i, y in enumerate(l):
        if y > x:
            return l[i - 1]

If nothing satisfies your search, it'll return None. If not sorted, call l.sort() before you do.

Upvotes: 4

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