Decompose a float into mantissa and exponent in base 10 without strings

Question

Are there functions in the Python library or numpy that take a float as input and return its decimal scientific notation decomposition, i.e. mantissa and exponent? Or is the

Answer 1

One way to avoid string conversions is to implement the methods using Decimals:

from decimal import Decimal

def fexp(number):
    (sign, digits, exponent) = Decimal(number).as_tuple()
    return len(digits) + exponent - 1

def fman(number):
    return Decimal(number).scaleb(-fexp(number)).normalize()

Note that using floating point numbers, its not possible to calculate mantissa and exponent without rounding. The reason is that floating point numbers are stored as base 2 fractions. For example stored float value for 154.3 is 154.30000000000001136868377216160297393798828125. Floats are displayed in console as accurate numbers, because (in CPython) they are always rounded when serialized using a hard-coded precision of 17.