Floating point issue

[afw2alan]

BPO	44910
Nosy	@ericvsmith

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-08-13.20:52:31.071>
created_at = <Date 2021-08-13.18:26:29.245>
labels = ['type-bug', 'invalid', '3.9']
title = 'Floating point issue'
updated_at = <Date 2021-08-13.21:18:38.319>
user = 'https://bugs.python.org/afw2alan'

bugs.python.org fields:

activity = <Date 2021-08-13.21:18:38.319>
actor = 'afw2alan'
assignee = 'none'
closed = True
closed_date = <Date 2021-08-13.20:52:31.071>
closer = 'eric.smith'
components = []
creation = <Date 2021-08-13.18:26:29.245>
creator = 'afw2alan'
dependencies = []
files = []
hgrepos = []
issue_num = 44910
keywords = []
message_count = 3.0
messages = ['399550', '399561', '399564']
nosy_count = 2.0
nosy_names = ['eric.smith', 'afw2alan']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue44910'
versions = ['Python 3.9']

[afw2alan]

0.01 + 273.15 should equal 273.16 but in python 3.9.5 or earlier report as 273.15999999999997.

[ericvsmith]

This a limitation of the floating point type that python uses. See https://docs.python.org/3/tutorial/floatingpoint.html

[afw2alan]

Eric,

I was unaware of this document and its implementation in python.

where
0.01+0.15 = 0.16 but 0.01+273.15=273.15999999999997

the latter which should be 273.16 which is triple point temperature of water in Kelvin.

This floating point variance explains some if the conditional test failures I have encountered.

regards

Alan

Get Outlook for Android<https://aka.ms/ghei36\>

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From: report=bugs.python.org@roundup.psfhosted.org <report=bugs.python.org@roundup.psfhosted.org> on behalf of Eric V. Smith <report@bugs.python.org>
Sent: Friday, 13 August 2021, 21:52
To: afw2alan@outlook.com
Subject: [bpo-44910] Floating point issue

Eric V. Smith <eric@trueblade.com> added the comment:

This a limitation of the floating point type that python uses. See https://docs.python.org/3/tutorial/floatingpoint.html

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nosy: +eric.smith
resolution: -> not a bug
stage: -> resolved
status: open -> closed

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Python tracker <report@bugs.python.org>
<https://bugs.python.org/issue44910\>

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