ENH: Add Series.str.casefold

[charlesdong1991]

• closes Series.str.casefold #25405
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[codecov]

Codecov Report

Merging #25419 into master will decrease coverage by 50.03%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master   #25419       +/-   ##
===========================================
- Coverage   91.73%    41.7%   -50.04%     
===========================================
  Files         173      173               
  Lines       52848    52850        +2     
===========================================
- Hits        48482    22040    -26442     
- Misses       4366    30810    +26444

Flag	Coverage Δ
#multiple	?
#single	41.7% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/strings.py	33.19% <100%> (-65.4%)	⬇️
pandas/io/formats/latex.py	0% <0%> (-100%)	⬇️
pandas/core/categorical.py	0% <0%> (-100%)	⬇️
pandas/io/sas/sas_constants.py	0% <0%> (-100%)	⬇️
pandas/tseries/plotting.py	0% <0%> (-100%)	⬇️
pandas/tseries/converter.py	0% <0%> (-100%)	⬇️
pandas/io/formats/html.py	0% <0%> (-99.35%)	⬇️
pandas/core/groupby/categorical.py	0% <0%> (-95.46%)	⬇️
pandas/io/sas/sas7bdat.py	0% <0%> (-91.17%)	⬇️
pandas/io/sas/sas_xport.py	0% <0%> (-90.15%)	⬇️
... and 132 more

---

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[codecov]

Codecov Report

Merging #25419 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #25419      +/-   ##
==========================================
+ Coverage   91.74%   91.75%   +0.01%     
==========================================
  Files         173      173              
  Lines       52923    52955      +32     
==========================================
+ Hits        48554    48589      +35     
+ Misses       4369     4366       -3

Flag	Coverage Δ
#multiple	90.32% <100%> (ø)	⬆️
#single	41.72% <100%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
pandas/core/strings.py	98.59% <100%> (ø)	⬆️
pandas/core/frame.py	96.85% <0%> (ø)	⬆️
pandas/core/indexes/category.py	98.61% <0%> (ø)	⬆️
pandas/core/groupby/generic.py	87% <0%> (+0.01%)	⬆️
pandas/io/json/json.py	93.22% <0%> (+0.08%)	⬆️
pandas/util/testing.py	87.66% <0%> (+0.09%)	⬆️
pandas/core/groupby/groupby.py	97.2% <0%> (+0.4%)	⬆️

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[gfyoung]

cc @jreback

[jreback]

needs a mention in text.rst (also there is a list of functions ) and in the references
and a whatsnew note

[jreback]

see comments

[charlesdong1991]

Thanks, @jreback I added it to text.rst as well as to reference/series.rst, I am not very sure which whatsnew note you refer to, I already added one in 0.25.0.rst, please let me know if you want it to move somewhere else.

[pep8speaks]

Hello @charlesdong1991! Thanks for updating the PR.

Cheers ! There are no PEP8 issues in this Pull Request. 🍻

Comment last updated on February 28, 2019 at 19:59 Hours UTC

[jreback]

Series.str has gained the :meth:`Series.str.casefold` method to ......(fill this in)

[charlesdong1991]

changed

[jreback]

can you add the versionadded 0.25.0 here (may need to add it to the dict to be formatted)

[charlesdong1991]

thanks, @jreback added!

[jreback]

can u verify this renders ok in the terminal

[charlesdong1991]

ahh, yeah, I printed the docstring, looks fine for me. @jreback

Convert strings in the Series/Index to be casefolded.

Equivalent to :meth:`str.casefold`.

Returns
-------
Series/Index of objects

See Also

Series.str.lower : Converts all characters to lowercase.
Series.str.upper : Converts all characters to uppercase.
Series.str.title : Converts first character of each word to uppercase and
remaining to lowercase.
Series.str.capitalize : Converts first character to uppercase and
remaining to lowercase.
Series.str.swapcase : Converts uppercase to lowercase and lowercase to
uppercase
Series.str.casefold: Removes all case distinctions in the string.
   .. versionadded:: 0.25.0

[WillAyd]

Does this render well on the web? Not aware of any other instance where the version added is in the See Also section. May be worth messing around with substitution to put it in the Summary

[charlesdong1991]

this rendering looks fine for me in the terminal. Since the summary of rendering only allows two parameters, and among these methods, only this Series.str.casefold is added in the new version. So i put this in the See also under Series.str.casefold. Otherwise, i assume the rendering might need to be changed.

[WillAyd]

You should be able to generate one HTML file rather easily:

https://python-sprints.github.io/pandas/guide/pandas_pr.html#visual-validation-of-the-docstring

If you can double check there would be preferable as majority of users will interface to docs via HTML.

[charlesdong1991]

sorry, do you have any idea why it's complaining AttributeError: type object 'StringMethods' has no attribute 'casefold'? is this quoting master? @WillAyd

[charlesdong1991]

btw, i tried something like below to put version added in the summary, but when i kind of manually inserting a blank line for other methods since they don't have version added issue. I would like to hear your advice on how to improve this? @WillAyd

    _shared_docs['casemethods'] = ("""
    Convert strings in the Series/Index to %(type)s.

    Equivalent to :meth:`str.%(method)s`.
    %(version)s

........

_shared_docs['casefold'] = dict(type='be casefolded', method='casefold',
                                    version='.. versionadded:: 0.25.0')

[WillAyd]

What are you running to get the AttributeError? As far as the second comment, probably easiest to add a newline(s) into the version argument

[jreback]

lgtm with some minor comments ping on green

[jreback]

not sure if these are ordered here - if they r alphabetic then this is not in the right place; otherwise maybe put next to lower

[charlesdong1991]

ok, the methods in series.rst is alphabetically ordered, here is not. But I will move it up a bit!

[jreback]

can u verify this renders ok in the terminal

[WillAyd]

Very minor nit but otherwise lgtm

[WillAyd]

Just call this expected

[charlesdong1991]

thanks, @WillAyd i just changed!

[charlesdong1991]

i change it a bit, now it looks like, do you prefer this? @WillAyd

    Convert strings in the Series/Index to casefolded.
    .. versionadded:: 0.25.0
    Equivalent to :meth:`str.casefold`.

    Returns
    -------
    Series/Index of objects

    See Also
    --------
    Series.str.lower : Converts all characters to lowercase.
    Series.str.upper : Converts all characters to uppercase.
    Series.str.title : Converts first character of each word to uppercase and
        remaining to lowercase.
    Series.str.capitalize : Converts first character to uppercase and
        remaining to lowercase.
    Series.str.swapcase : Converts uppercase to lowercase and lowercase to
        uppercase.
    Series.str.casefold: Removes all case distinctions in the string.

[jreback]

lgtm. over to you @WillAyd

[WillAyd]

@charlesdong1991 does that render correctly in HTML? Might need a blank line before versionadded

[charlesdong1991]

somehow, i still get this error when running python make.py html --single pandas.Series.str.casefold, is it because of str.casefold not in python2? @WillAyd

Traceback (most recent call last):
  File "make.py", line 79, in _process_single_doc
    obj = getattr(obj, name)
AttributeError: type object 'StringMethods' has no attribute 'casefold'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "make.py", line 339, in <module>
    sys.exit(main())
  File "make.py", line 334, in main
    args.verbosity, args.warnings_are_errors)
  File "make.py", line 46, in __init__
    single_doc = self._process_single_doc(single_doc)
  File "make.py", line 81, in _process_single_doc
    raise ImportError('Could not import {}'.format(single_doc))
ImportError: Could not import pandas.Series.str.casefold

And i was thinking to add a blank line in-between, however, for all other methods, there will be two blank lines, and i don't think it's good...

Convert strings in the Series/Index to lower.


Equivalent to :meth:`str.lower`.

[WillAyd]

Not sure the distinction you are trying to make with Python2 - are you actively developing with that?

Otherwise do the other methods produce something for you? I would think should work the same as the rest. As far as the blank lines go can just add a "\n" preceding the argument

[charlesdong1991]

i distinguish python 2 is because str.casefold is only valid in python3+ if i am not wrong.

It's quite wired that all other methods work fine, but this new added one... and only this is valid only in python3, so i made a guess of where it might go wrong to get this error @WillAyd

And i add \n to make new lines, thanks!

[WillAyd]

Looks like an issue in the make file which is causing it to pick up another pandas installation on your computer which obviously wouldn't have that attribute yet. I patched locally just to make sure so here's the doc:

lgtm

[WillAyd]

Thanks @charlesdong1991 nice work!