[Patches] [ python-Patches-1602128 ] clarify comparison return values
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Tue Mar 6 19:30:23 CET 2007
Patches item #1602128, was opened at 2006-11-24 07:24
Message generated for change (Comment added) made by gbrandl
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Category: Documentation
Group: Python 2.4
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Jim Jewett (jimjjewett)
Assigned to: Nobody/Anonymous (nobody)
Summary: clarify comparison return values
Initial Comment:
In the Language Reference section 3.4.1 (http://docs.python.org/ref/customization.html for version 2.5), in the first paragraph where it describes __lt__, __le__, __eq__, __ne__, __gt__, and __ge__,
It should mention the special case of NotImplemented, so that people will not be reluctant to return it. (The fourth paragraph suggests returning NotImplemented, but the first suggests that *any* return value will be converted to a boolean, so that NotImplented would mean "True")
Please change:
"""These methods can return any value, but if the comparison operator is used in a Boolean context, the return value should be interpretable as a Boolean value, else a TypeError will be raised. By convention, False is used for false and True for true."""
to:
"""When an object does not know how to compute a meaningful result, it should return the singleton NotImplemented, in case the other object implements the reflected comparison.
By convention, a successful comparison should return either True or False. If any other object is returned in a Boolean context, python will implicitly call bool(result).
"""
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>Comment By: Georg Brandl (gbrandl)
Date: 2007-03-06 18:30
Message:
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user_id=849994
Originator: NO
Fixed in rev. 54171, 54172 (2.5).
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