Function negate_python 

pub fn negate_python(number: Decimal) -> Decimal

Negate with Python decimal’s sign rule for zero.

Python defines unary minus as 0 - x, so negating ANY zero yields a POSITIVE zero:

  -Decimal("0.00")   ==  0.00
  -Decimal("-0.00")  ==  0.00

rust_decimal’s Neg flips the sign bit unconditionally, so -dec!(0.00) is a signed zero that renders -0.00. beancount normalizes it away — a ledger posting written -0.00 CNY loads as Decimal('0.00') there, and bean-query prints 0.00 — while rledger’s parser applies the sign with a bare -n and kept the -0.00 all the way to the output.

A zero has no sign in bookkeeping; this is the canonical negation for any site that flips a parsed or computed amount.