Add programming FAQ entry: remove multiple entries from list

[sreedeviha]

BPO	41774
Nosy	@rhettinger, @terryjreedy, @pfmoore, @ericvsmith, @stevendaprano, @miss-islington
PRs	bpo-41774: Add programming FAQ entry #22402 [3.9] bpo-41774: Add programming FAQ entry (GH-22402) #22447 [3.8] bpo-41774: Add programming FAQ entry (GH-22402) #22448 bpo-41774: Tweak new programming FAQ entry #22562 [3.9] bpo-41774: Tweak new programming FAQ entry (GH-22562) #22563 [3.8] bpo-41774: Tweak new programming FAQ entry (GH-22562) #22564
Files	listrepxxx.py: Program to remove 20 from list

^{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 = 'https://github.com/terryjreedy'
closed_at = <Date 2020-10-05.15:16:04.912>
created_at = <Date 2020-09-12.16:20:35.749>
labels = ['type-feature', '3.8', '3.9', '3.10', 'docs']
title = 'Add programming FAQ entry: remove multiple entries from list'
updated_at = <Date 2020-10-05.15:16:04.911>
user = 'https://bugs.python.org/sreedeviha'

bugs.python.org fields:

activity = <Date 2020-10-05.15:16:04.911>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = True
closed_date = <Date 2020-10-05.15:16:04.912>
closer = 'terry.reedy'
components = ['Documentation']
creation = <Date 2020-09-12.16:20:35.749>
creator = 'sreedevi.ha'
dependencies = []
files = ['49454']
hgrepos = []
issue_num = 41774
keywords = ['patch']
message_count = 23.0
messages = ['376803', '376804', '376805', '376806', '376807', '376808', '376810', '376822', '377456', '377464', '377471', '377477', '377478', '377484', '377486', '377497', '377654', '377655', '377656', '377673', '378034', '378037', '378038']
nosy_count = 7.0
nosy_names = ['rhettinger', 'terry.reedy', 'paul.moore', 'eric.smith', 'steven.daprano', 'miss-islington', 'sreedevi.ha']
pr_nums = ['22402', '22447', '22448', '22562', '22563', '22564']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue41774'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[sreedeviha]

Define a list which has all same elements.
While removing the same element from list using for loop and by using remove() method, output should be empty list, but the output we get is one element is unremoved

[ericvsmith]

You should not mutate a list while iterating over it.

See, for example https://stackoverflow.com/questions/6260089/strange-result-when-removing-item-from-a-list

I couldn't find a place where this is mentioned in the python list docs. If it's not there, we should add something to the programming FAQ.