drop trailing zeros from decimal

Question

I have a long list of Decimals and that I have to adjust by factors of 10, 100, 1000,..... 1000000 depending on certain conditions. When I multiply them there is sometimes

Answer 1

Slightly modified version of A-IV's answer

NOTE that Decimal('0.99999999999999999999999999995').normalize() will round to Decimal('1')

def trailing(s: str, char="0"):
    return len(s) - len(s.rstrip(char))

def decimal_to_str(value: decimal.Decimal):
    """Convert decimal to str

    * Uses exponential notation when there are more than 4 trailing zeros
    * Handles decimal.InvalidOperation
    """
    # to_integral_value() removes decimals
    if value == value.to_integral_value():
        try:
            value = value.quantize(decimal.Decimal(1))
        except decimal.InvalidOperation:
            pass
        uncast = str(value)
        # use exponential notation if there are more that 4 zeros
        return str(value.normalize()) if trailing(uncast) > 4 else uncast
    else:
        # normalize values with decimal places
        return str(value.normalize())
        # or str(value).rstrip('0') if rounding edgecases are a concern