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classification
Title: cross-type comparison is different in python minor versions
Type: behavior Stage: resolved
Components: Interpreter Core Versions: Python 3.4
process
Status: closed Resolution: not a bug
Dependencies: Superseder:
Assigned To: Nosy List: r.david.murray, secalert
Priority: normal Keywords:

Created on 2015-03-09 10:35 by secalert, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Files
File name Uploaded Description Edit
python-float-decimal-comparison.txt secalert, 2015-03-09 10:35
Messages (2)
msg237632 - (view) Author: David Vieira-Kurz (secalert) Date: 2015-03-09 10:35
Python internal compare function does not verify if a comparison of two objects is done by using object of the same type.

In this case python does not know how to compare DECIMAL and FLOATS and returns a FALSE instead of returning an Error.

Python should have strict rules to only allow comparison between objects is aware of but depending on the version of Python we have different behaviors:

# Output:
# Python 2.6.5 32bit -- WRONG: FLOAT seems comparable with DECIMAL (WRONG)
# Python 2.7.2 32bit -- WRONG: FLOAT seems comparable with DECIMAL (WRONG)
# Python 3.1.2 32bit -- CORRECT: FLOAT is NOT comparable with DECIMAL (CORRECT)
# Python 3.4.0 ([GCC 4.8.2] on linux) 32bit -- WRONG: FLOAT seems comparable with DECIMAL (WRONG)

A proof of concept code-snippet is attached.
msg237644 - (view) Author: R. David Murray (r.david.murray) * (Python committer) Date: 2015-03-09 13:14
In Python2, all objects were comparable (except DateTime stuff...and maybe there was one other exception, I forget).  We did indeed decide this was a bug and fixed it in Python3.  Now objects of different types are comparable if only if at least one of them supports being compared with the other.  Python does, however, know how to compare Float and Decimal correctly, since Python 3.2 (see the What's New document for Python 3.2).
History
Date User Action Args
2022-04-11 14:58:13adminsetgithub: 67808
2015-03-09 13:14:03r.david.murraysetstatus: open -> closed

nosy: + r.david.murray
messages: + msg237644

resolution: not a bug
stage: resolved
2015-03-09 10:35:47secalertcreate