ieee 754 conversion function

Has some bugs

// Some code
# 'dataset' holds the input data for this script
import pandas as pd

def ieee_754_conversion(n, sgn_len=1, exp_len=8, mant_len=23):
    if n >= 2 ** (sgn_len + exp_len + mant_len):
        raise ValueError("Number n is longer than prescribed parameters allows")

    sign = (n & (2 ** sgn_len - 1) * (2 ** (exp_len + mant_len))) >> (exp_len + mant_len)
    exponent_raw = (n & ((2 ** exp_len - 1) * (2 ** mant_len))) >> mant_len
    mantissa = n & (2 ** mant_len - 1)

    sign_mult = 1
    if sign == 1:
        sign_mult = -1

    if exponent_raw == 2 ** exp_len - 1:  # Could be Inf or NaN
        if mantissa == 2 ** mant_len - 1:
            return float('nan')  # NaN

        return sign_mult * float('inf')  # Inf

    exponent = exponent_raw - (2 ** (exp_len - 1) - 1)

    if exponent_raw == 0:
        mant_mult = 0  # Gradual Underflow
    else:
        mant_mult = 1

    for b in range(mant_len - 1, -1, -1):
        if mantissa & (2 ** b):
            mant_mult += 1 / (2 ** (mant_len - b))

    return sign_mult * (2 ** exponent) * mant_mult

## DEC = high * 65536 + low  

for i in range(0, len(dataset)):
   dataset.loc[i,'HumidityValue'] = ieee_754_conversion(dataset.loc[i,'HumidityDEC'], exp_len=8, mant_len=23)