Checking if two values are approximately the same in python

Question

I have two functions which give me very small numbers. I want to define a IF statements in which If two values are approximately the same print them otherwise pass

a = (x, y)
b = (h, p)
If a == b:
   print(a, b)
else:
   pass

for this we cannot use ==. How to define it to be close? Because the order of values maybe like a=7e-25, b=1.5e-26

how much is your approximation range ? 100, 1000 , 2, 3 ? how much ? — moh80s, Dec 17 '19 at 09:14
@MohVahedi What do you mean? The preference is to find closest value — Ma Y, Dec 17 '19 at 09:15
decide eps value constant say `eps = 0.0001` then you can compare absolute diff `a` and `b` is less than `eps`...`|a-b| < eps` — Dishin H Goyani, Dec 17 '19 at 09:18

Filip Młynarski · Answer 1 · 2019-12-17T09:37:59.253

1

You could use math.isclose().

from math import isclose
a = 1.0
b = 1.00000001
print(isclose(a, b, abs_tol=1e-8))  # -> True

[Comment update] If you want to find value of a list that is closest to some value, here's example solution

a = 7e-25
b = [1.5e-26,1.4e-26,1.3e-26,1.4e-26,1.5e-27]
print(min(b, key=lambda x: abs(a-x)))  # -> 1.5e-26

edited Dec 17 '19 at 09:37

answered Dec 17 '19 at 09:17

Filip Młynarski

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One thing that I cannot under stand is, How I can find closest value between these `a = 7e-25 b = [1.5e-26,1.4e-26,1.3e-26,1.4e-26,1.5e-27]` it should be `1.5e-26` – Ma Y Dec 17 '19 at 09:23
Is there any way? – Ma Y Dec 17 '19 at 09:29
why it doesnt work inside the if statement? – Ma Y Dec 17 '19 at 09:44
How your if statement looks like? – Filip Młynarski Dec 17 '19 at 09:47
`for bb in range(len(b)): `,`if (min(b[bb], key=lambda x: abs(a-x))):`,`print(print(a,b[bb]))` – Ma Y Dec 17 '19 at 09:50
and ofcourse I have no list, the values of `b` come from another for loop – Ma Y Dec 17 '19 at 09:52

score 0 · Answer 2 · answered Dec 17 '19 at 09:17

0

Use the numpy function isclose:

import numpy as np
a = 7e-25
b = 1.5e-26
if np.isclose(a, b):
    print(a, b)

answered Dec 17 '19 at 09:17

Rob

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One thing that I cannot under stand is, How I can find closest value between these `a = 7e-25 b = [1.5e-26,1.4e-26,1.3e-26,1.4e-26,1.5e-27]` it should be `1.5e-26` – Ma Y Dec 17 '19 at 09:25
That's a different question, feel free to ask a new question about that. – Rob Dec 17 '19 at 09:33

Checking if two values are approximately the same in python

2 Answers2