Extracting the exponent from scientific notation

Question

I have a bunch of numbers in scientific notation and I would like to find their exponent. For example:

>>> find_exp(3.7e-13)
13

>>> find_exp(-7.2e-11)
11

Hence I only need their exponent ignoring everything else including the sign.

I have looked for such a way in python but similar questions are only for formatting purposes.

Madera

why dont you convert them to a string as they are. Then use regex to extract the last part after the dash. Then you can convert back to number. – Mamiemamma

that is not an option. Likewise, I could have split the string after converting it to a regular float – Madera

And why is it not an option? Also splitting on the dash would be a bit shaky because it could be signed with a minus and unsigned. You would need to include this in your check. – Mamiemamma

It seems the input is already in string format (cf. the quotes). – Boudreau

What are some of the other strings you have? Do some have more than one digit before the decimal point, like "26.3e-10", or is the notation always normalized? Secondly, what would be the answer for "1.1111111111e2"? – Boudreau

Answer 1

Common logarithm is what you need here, you can use log10 + floor:

from math import log10, floor

def find_exp(number) -> int:
    base10 = log10(abs(number))
    return abs(floor(base10))

find_exp(3.7e-13)
# 13

find_exp(-7.2e-11)
# 11

Georgeta