Description

assignee = None
closed_at = <Date 2015-12-11.15:45:34.289>
created_at = <Date 2015-12-11.15:02:00.929>
labels = ['type-feature']
title = 'Allow `False` to be passed to `filter`'
updated_at = <Date 2015-12-11.19:54:59.059>
user = 'https://github.com/leewz'

activity = <Date 2015-12-11.19:54:59.059>
actor = 'leewz'
assignee = 'none'
closed = True
closed_date = <Date 2015-12-11.15:45:34.289>
closer = 'r.david.murray'
components = []
creation = <Date 2015-12-11.15:02:00.929>
creator = 'leewz'
dependencies = []
files = []
hgrepos = []
issue_num = 25840
keywords = []
message_count = 4.0
messages = ['256218', '256219', '256222', '256231']
nosy_count = 3.0
nosy_names = ['r.david.murray', 'leewz', 'abarry']
pr_nums = []
priority = 'normal'
resolution = 'rejected'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue25840'
versions = ['Python 3.6']

Activity

1. leewz commented on Dec 11, 2015

   

   leewzmannequin

   on Dec 11, 2015

   MannequinAuthor

   More actions

   Meaning:

       filter(False, lst)
       == (x for x in lst if not x)
       == itertools.filterfalse(None, lst)

   I understand that it is a very minor enhancement, and with not much benefit. I just happened to think about it, and wondered why it didn't already exist. I figured it wouldn't hurt to put the idea out here.

   (If anyone is interested, I was looking into ways that filter/map/itertools could "unwrap" each other at the C level to improve composition of generators, inspired by the functools.partial optimization.)
2. leewz

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Dec 11, 2015
3. Vgr255 commented on Dec 11, 2015

   

   Vgr255mannequin

   on Dec 11, 2015

   Mannequin

   More actions

   Do you mean like 'filter(None, lst)' does?
4. bitdancer commented on Dec 11, 2015

   

   bitdancer

   on Dec 11, 2015

   Member

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   I don't think it is worth adding as a special case. Itertools has it because of what itertools is (a mini-language for manipulating iterables), but the legacy filter function has no reason to grow additional special cases beyond None. (It's not even clear why it has that one special case :)
5. bitdancer

   closed this as completedon Dec 11, 2015
6. leewz commented on Dec 11, 2015

   

   leewzmannequin

   on Dec 11, 2015

   MannequinAuthor

   More actions

   ebarry, note that filter(None, lst) is equivalent to filter(bool, lst), which is the opposite of filterfalse(None, lst). (Though filter(True, lst) == filter(bool, lst) would be a parallel.)
7. ezio-melotti

   transferred this issue fromon Apr 10, 2022

Issue actions