35.5 - 29.58 = 5.920000000000002 (it's false !)

[Hogren]

BPO	28285
Nosy	@serhiy-storchaka

^{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 2016-09-27.10:18:42.008>
created_at = <Date 2016-09-27.10:13:55.009>
labels = ['type-bug', 'invalid']
title = "35.5 - 29.58 = 5.920000000000002 (it's false !)"
updated_at = <Date 2016-09-27.10:18:42.006>
user = 'https://bugs.python.org/Hogren'

bugs.python.org fields:

activity = <Date 2016-09-27.10:18:42.006>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2016-09-27.10:18:42.008>
closer = 'serhiy.storchaka'
components = []
creation = <Date 2016-09-27.10:13:55.009>
creator = 'Hogren'
dependencies = []
files = []
hgrepos = []
issue_num = 28285
keywords = []
message_count = 2.0
messages = ['277511', '277512']
nosy_count = 2.0
nosy_names = ['serhiy.storchaka', 'Hogren']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue28285'
versions = ['Python 2.7', 'Python 3.3', 'Python 3.4']

[Hogren]

I was using python as calculator when I enter :
35.5 - 29.58

I am surprising when python give me a result with many decimals:
5.920000000000002

I tried to change one number :
35.5 - 29.57
The result is correct : 5.93

The error is present again when I tried to inverse numbers (29.57-35.5).

The error is again present when I tried to use 35.50 in place of 35.5.

I tested on python 2.7 and 3.4, compiled with gcc 4.9.3, on Gentoo.

Thanks for all who contribute to this good project which is Python !

Hogren

[serhiy-storchaka]

https://docs.python.org/3/tutorial/floatingpoint.html