[New-bugs-announce] [issue21540] PEP 8 should recommend "is not" and "not in"

Florent Xicluna report at bugs.python.org
Tue May 20 07:59:44 CEST 2014

New submission from Florent Xicluna:

Python accepts both syntaxes:

    if not item in some_list and not item is None:
        return item


    if item not in some_list and item is not None:
        return item

In the first form, you identify 5 operators: "not", "in", "and", "not" and "in"
In the second form, you find only 3 operators: "not in", "and", "is not"

Of course CPython does internal optimization, and it compiles both expressions to the same bytecode.

However the second form is more readable and less error-prone. It is plain English.

I propose to add such advice to the section "Programming Recommendations" of PEP 8.

assignee: docs at python
components: Documentation
messages: 218837
nosy: barry, docs at python, flox, ncoghlan
priority: normal
severity: normal
status: open
title: PEP 8 should recommend "is not" and "not in"
type: enhancement

Python tracker <report at bugs.python.org>

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