Find the nearest number(but not exceed) in the list and change numbers in the series(Python)

Question

there is a series like below

s = pd.Series([25, 33, 39])

0    25
1    33
2    39
dtype: int64

and a list

list = [5, 10, 20, 26, 30, 31, 32, 35, 40]

[5, 10, 20, 26, 30, 31, 32, 35, 40]

I’d like to find the nearest number in the list and **change the number **in the series

for example
first number is the series is 25
but the list is [5, 10, 20, 26, 30, 31, 32, 35, 40]

so the firtst nearest number(corresponding to 25 in the series)
is 20 (Actually 26 is nearest number, but I need a number less than 25)

and then the second number is 31, thrid is 35
after finding the number and change that in the series

desired out s is

0    20
1    31
2    35

please give me advice. It’s a very important task for me.
if possilbe? without for loop plz

Find the nearest number(but not exceed) in the list and change numbers in the series(Python)

Asked By: ghost_like

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Answer 1

You are looking for merge_asof:

s = pd.Series([25, 33, 39], name="s")
l = pd.Series([5, 10, 20, 26, 30, 31, 32, 35, 40], name="l")

pd.merge_asof(s, l, left_on="s", right_on="l")

A few notes:

There is a bug in your expected output. The closest number to 33 is 32.
Don’t name your variable list. It overwrites the name of a very common Python class.
Make sure l is sorted.

Question: