Problem in join function definition

[yseb]

BPO	1120862
Nosy	@rhettinger

^{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 = None
closed_at = <Date 2005-02-12.19:22:44.000>
created_at = <Date 2005-02-11.15:43:00.000>
labels = ['invalid', 'docs']
title = 'Problem in join function definition'
updated_at = <Date 2005-02-12.19:22:44.000>
user = 'https://bugs.python.org/yseb'

bugs.python.org fields:

activity = <Date 2005-02-12.19:22:44.000>
actor = 'rhettinger'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2005-02-11.15:43:00.000>
creator = 'yseb'
dependencies = []
files = []
hgrepos = []
issue_num = 1120862
keywords = []
message_count = 3.0
messages = ['24262', '24263', '24264']
nosy_count = 3.0
nosy_names = ['effbot', 'rhettinger', 'yseb']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1120862'
versions = ['Python 2.5']

[yseb]

There is a problem in the last sentence of the join
definition.

==========================================

join( words[, sep]) 

Concatenate a list or tuple of words with intervening
occurrences of sep. The default value for sep is a single
space character. It is always true that "string.join
(string.split(s, sep), sep)" equals s.
==========================================

It is true that string.join(string.split(s, sep), sep)" is
always equals to s.

But string.join(string.split(s)) is not always equals to s
especially for repeated sequence of spaces.

[effbot]

Logged In: YES
user_id=38376

And? If the documentation explains how something works,
does it also have to list a couple of other things that doesn't
work?

[rhettinger]

Logged In: YES
user_id=80475

I concur.  The sentence is correct:
>>> s = '  the quick    brown \t\t fox jumped  '
>>> sep = ' '
>>> s == string.join(string.split(s, sep), sep)
True

Possibly the docs could go on to talk about
string.join(string.split(s)). However that would just be
adding rambling verbiage that is unlikely to be helpful to
anyone who has just read what string.split(s) actually does.