From 2450be607cfbdb1ab9e4ed7c0fe01d715e406d18 Mon Sep 17 00:00:00 2001 From: Sergey B Kirpichev Date: Tue, 16 Dec 2025 14:41:59 +0300 Subject: [PATCH] decimal docs: specification link and examples (#128698) Co-authored-by: RUANG (James Roy) Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com> Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com> --- Doc/library/decimal.rst | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst index 621aa23ecc80..376bcc7aaf9e 100644 --- a/Doc/library/decimal.rst +++ b/Doc/library/decimal.rst @@ -34,10 +34,12 @@ The :mod:`decimal` module provides support for fast correctly rounded decimal floating-point arithmetic. It offers several advantages over the :class:`float` datatype: -* Decimal "is based on a floating-point model which was designed with people - in mind, and necessarily has a paramount guiding principle -- computers must - provide an arithmetic that works in the same way as the arithmetic that - people learn at school." -- excerpt from the decimal arithmetic specification. +* Decimal "is based on a `floating-point model + `__ which was designed + with people in mind, and necessarily has a paramount guiding principle -- + computers must provide an arithmetic that works in the same way as the + arithmetic that people learn at school." -- excerpt from the decimal + arithmetic specification. * Decimal numbers can be represented exactly. In contrast, numbers like ``1.1`` and ``2.2`` do not have exact representations in binary @@ -238,6 +240,26 @@ floating-point flying circus: >>> c % a Decimal('0.77') +Decimals can be formatted (with :func:`format` built-in or :ref:`f-strings`) in +fixed-point or scientific notation, using the same formatting syntax (see +:ref:`formatspec`) as builtin :class:`float` type: + +.. doctest:: + + >>> format(Decimal('2.675'), "f") + '2.675' + >>> format(Decimal('2.675'), ".2f") + '2.68' + >>> f"{Decimal('2.675'):.2f}" + '2.68' + >>> format(Decimal('2.675'), ".2e") + '2.68e+0' + >>> with localcontext() as ctx: + ... ctx.rounding = ROUND_DOWN + ... print(format(Decimal('2.675'), ".2f")) + ... + 2.67 + And some mathematical functions are also available to Decimal: >>> getcontext().prec = 28 -- 2.47.3