From c60394c7fc9cc09b16e9675a3eeb5844b6d8523f Mon Sep 17 00:00:00 2001 From: kpinc Date: Wed, 21 Oct 2020 12:13:50 -0500 Subject: [PATCH] bpo-39416: Document some restrictions on the default string representations of numeric classes (GH-18111) [bpo-39416](): Document string representations of the Numeric classes This is a change to the specification of the Python language. The idea here is to put sane minimal limits on the Python language's default representations of its Numeric classes. That way "Marty's Robotic Massage Parlor and Python Interpreter" implementation of Python won't do anything too crazy. Some discussion in the email thread: Subject: Documenting Python's float.__str__() https://mail.python.org/archives/list/python-dev@python.org/thread/FV22TKT3S2Q3P7PNN6MCXI6IX3HRRNAL/ --- Doc/reference/datamodel.rst | 18 ++++++++++++++++++ .../2020-01-22-05-14-53.bpo-39416.uYjhEm.rst | 1 + 2 files changed, 19 insertions(+) create mode 100644 Misc/NEWS.d/next/Documentation/2020-01-22-05-14-53.bpo-39416.uYjhEm.rst diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 29e64cba2ca..d9b72a9a942 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -187,6 +187,24 @@ Ellipsis related to mathematical numbers, but subject to the limitations of numerical representation in computers. + The string representations of the Numeric classes, computed by + :meth:`__repr__` and :meth:`__str__`, have the following + properties: + + * They are valid numeric literals which, when passed to their + class constructor, produce an object having the value of the + original numeric. + + * The representation is in base 10, when possible. + + * Leading zeros, possibly excepting a single zero before a + decimal point, are not shown. + + * Trailing zeros, possibly excepting a single zero after a + decimal point, are not shown. + + * A sign is shown only when the number is negative. + Python distinguishes between integers, floating point numbers, and complex numbers: diff --git a/Misc/NEWS.d/next/Documentation/2020-01-22-05-14-53.bpo-39416.uYjhEm.rst b/Misc/NEWS.d/next/Documentation/2020-01-22-05-14-53.bpo-39416.uYjhEm.rst new file mode 100644 index 00000000000..279a5f18ff8 --- /dev/null +++ b/Misc/NEWS.d/next/Documentation/2020-01-22-05-14-53.bpo-39416.uYjhEm.rst @@ -0,0 +1 @@ +Document some restrictions on the default string representations of numeric classes.