Add textwrap.dedent, .indent, as str methods.

[terryjreedy]

BPO	18335
Nosy	@warsaw, @terryjreedy, @ncoghlan, @ezio-melotti, @merwok, @Julian, @ericsnowcurrently, @vadmium, @serhiy-storchaka

^{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 = None
created_at = <Date 2013-07-01.05:33:49.321>
labels = ['type-feature']
title = 'Add textwrap.dedent, .indent, as str methods.'
updated_at = <Date 2013-09-01.01:58:54.523>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2013-09-01.01:58:54.523>
actor = 'martin.panter'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2013-07-01.05:33:49.321>
creator = 'terry.reedy'
dependencies = []
files = []
hgrepos = []
issue_num = 18335
keywords = []
message_count = 7.0
messages = ['192109', '192114', '192115', '192116', '192133', '192148', '196696']
nosy_count = 12.0
nosy_names = ['barry', 'terry.reedy', 'ncoghlan', 'ezio.melotti', 'eric.araujo', 'cvrebert', 'Julian', 'tshepang', 'eric.snow', 'martin.panter', 'serhiy.storchaka', 'SpaghettiToastBook']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue18335'
versions = ['Python 3.4']

[terryjreedy]

To end proposals for new syntax to do what they do for triple-quoted strings. Nick Coghlan gave reasons as follows: run time cost small, can be optimized away, would be used more than some other string methods.
http://mail.python.org/pipermail/python-ideas/2013-July/021717.html

In response, Guido said "That's a compelling argument. Let's do it."
http://mail.python.org/pipermail/python-ideas/2013-July/021718.html

[ncoghlan]

It turns out there's one slight wrinkle in this grand plan: it won't work for docstrings without some additional tweaking to allow for method calls in the docstring detection.

>>> def f():
...     """example""".lower()
... 
>>> print(f.__doc__)
None
>>> import dis
>>> dis.dis(f)
  2           0 LOAD_CONST               1 ('example') 
              3 LOAD_ATTR                0 (lower) 
              6 CALL_FUNCTION            0 (0 positional, 0 keyword pair) 
              9 POP_TOP              
             10 LOAD_CONST               0 (None) 
             13 RETURN_VALUE

[ncoghlan]

I still think the methods are worth adding regardless - I just anticipate a request to allow method calls on docstrings to follow not long after ;)

[serhiy-storchaka]

str already have too many methods. Who uses str.swapcase() or str.zfill() now? I'm -0.5 for adding any new str methods.

[warsaw]

.dedent() is a no-brainer. JFDI. +1

.indent() I guess makes sense for symmetry, although I've rarely used it. -0

As for docstrings, I can imagine other alternatives, so let's let someone interested in that go through the PEP process.

[merwok]

IMO it’s fine that docstrings continue to live as pure string literals, and documentation tools continue to follow PEP-257’s advice.

[vadmium]

If this goes ahead, would a bytes.dedent() method be also considered? I recently discovered that textwrap.dedent() does not work on bytes() in Python 3. I would have used it for the contents of an input file in a test case.

For the record there’s an older bpo-1237680 on this, rejected in 2005.

[methane]

#81087 is a relating issue.

[methane]

I implemented compile time cleandoc in #106411.
So this issue should be focus on str.dedent() and bytes.dedent().

textwrap.dedent() is complex function. I want to make str.dedent() much simpler.

• remove only whitespace -- user need to use textwrap.dedent() to support TAB indent
  • If we want to support TAB, we will add option later.
• both of bytes.dedent() and str.dedent() use same char* based logic -- str.dedent() uses utf-8. This minimize our maintenance cost.

[methane]

I created a poll on discuss.python.org for naming.
https://discuss.python.org/t/str-dedent-vs-str-removeindent/30127

[ofek]

What is the status of this?

[methane]

I need to write a PEP for this. But I don't have time for it for now.