round a float to a defined number of significant digits

significant_number_round.py

def round_significant(number, nsig):
    from math import log10
    if number != 0:
        lg10 = int((log10(abs(number))))
        if abs(number) < 1:
            lg10 -= 1
        ndig = nsig - lg10 - 1
        rded = round(number, ndig)
        if ndig <= 0:
            rded = int(rded)

        return rded
    else:
        return int(number)