python convert 123.456 to 0.123456

i want convert the float to [0.something] but my data have very different numbers like

123.456,
12.3456,
1234.56

i know i can do

ConvertNum = 123.456
convertNum /= 1000
print(convertNum)

but my problem is if when i don’t know how many 10 multiplication i need to make it 0.something

so i tried something like this

ConvertNum = 123.456
convertStr = str(ConvertNum).split(".")
convertStr = f"0.{convertStr[0] + convertStr[1]}"
print(float(convertStr))

but my question is, is this the best way to do that?

is there any function like in math library that can do it automatically?

>Solution :

Use maths… The number of whole digits in a number can be found using log:

from math import ceil, log10

def normalize(a):
    return a / 10 ** ceil(log10(a))

Test cases:

>>> print(normalize(1.23))
0.123

>>> print(normalize(123.45))
0.12345

>>> print(normalize(0.1))
0.1