Prices, quantities and exact decimals

import re

def decimal_parts(value: str) -> tuple[str, int]:
    if not isinstance(value, str) or len(value) > 160:
        raise ValueError("Use a bounded fixed-decimal string")
    if re.fullmatch(r"-?[0-9]+(?:\.[0-9]+)?", value) is None:
        raise ValueError("Use digits with an optional decimal point")
    negative = value.startswith("-")
    whole, _, fraction = value.lstrip("-").partition(".")
    scale = len(fraction)
    coefficient = (whole + fraction).lstrip("0") or "0"
    if scale > 30 or len(coefficient) > 128:
        raise ValueError("Value exceeds the wire precision bounds")
    if negative and coefficient != "0":
        coefficient = "-" + coefficient
    return coefficient, scale

price_atomic, price_scale = decimal_parts("70123.45")
quantity_atomic, quantity_scale = decimal_parts("0.001")
request_rows = {
    "open_prices_atomic": [price_atomic],
    "open_prices_scale": [price_scale],
    "open_quantities_atomic": [quantity_atomic],
    "open_quantities_scale": [quantity_scale],
}