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DOC: Improve the docstring of String.str.zfill() #20864

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Merged
merged 8 commits into from
Jul 7, 2018
Merged

DOC: Improve the docstring of String.str.zfill() #20864

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1e16540
DOC: Improve the docstring of String.str.zfill()
alkamid Apr 29, 2018
b89cd54
Fix PEP8 errors
alkamid Apr 29, 2018
6669889
Merge branch 'master' into docstring_series_str_zfill
alkamid Apr 30, 2018
07f4189
Correct language, add more concise example
alkamid Apr 30, 2018
8034856
Fix PEP8 errors
alkamid Apr 30, 2018
60ea781
Explain behaviour in the example
alkamid May 2, 2018
4a54a66
Merge remote-tracking branch 'upstream/master' into docstring_series_…
alkamid May 2, 2018
706688f
Merge remote-tracking branch 'upstream/master' into alkamid-docstring…
TomAugspurger Jul 7, 2018
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51 changes: 46 additions & 5 deletions pandas/core/strings.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2114,19 +2114,60 @@ def rjust(self, width, fillchar=' '):

def zfill(self, width):
"""
Filling left side of strings in the Series/Index with 0.
Equivalent to :meth:`str.zfill`.
Pad strings in the Series/Index by prepending '0' characters.

Strings in the Series/Index are padded with '0' characters on the
left of the string to reach a total string length `width`. Strings
in the Series/Index with length greater or equal to `width` are
unchanged.

Parameters
----------
width : int
Minimum width of resulting string; additional characters will be
filled with 0
Minimum length of resulting string; strings with length less
than `width` be prepended with '0' characters.

Returns
-------
filled : Series/Index of objects
Series/Index of objects

See Also
--------
Series.str.rjust: Fills the left side of strings with an arbitrary
character.
Series.str.ljust: Fills the right side of strings with an arbitrary
character.
Series.str.pad: Fills the specified sides of strings with an arbitrary
character.
Series.str.center: Fills boths sides of strings with an arbitrary
character.

Notes
-----
Differs from :meth:`str.zfill` which has special handling
for '+'/'-' in the string.

Examples
--------
>>> s = pd.Series(['-2', '+5', '10', '423523', 127, np.nan])
>>> s
0 -2
1 +5
2 10
3 423523
4 127
5 NaN
dtype: object
>>> s.str.zfill(5)
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Looks great now. Just couple of ideas, feel free to ignore them if you prefer the way it is now.

I think it could be useful to add a short paragraph before this line explaining that the non-string values (127 and NaN) become NaN, and may be reemphasizing what you already have in the body of the docstring, that the values with sign (-2 and +5) get the zeros in the left of the sign, and that 423523 keeps unchanged as it's longer than width.

I also think that it would make things easier/faster to understand if the values look a bit less arbitrary. For example ['-1', '1', 10, np.nan, '1000'] (with a width of 3 in this example).

0 000-2
1 000+5
2 00010
3 423523
4 NaN
5 NaN
dtype: object
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the example looks cool, but I think we can make it a bit more compact and clear by:

  • Just creating a single Series (I'd get rid of one of 10 or 127 as they show the same user case, and I'd add a NaN and a number (as number, not as string).
  • After creating the Series I'd show it without modification (i.e. >>> s). This makes the result easier to compare with the original data.
  • We can get rid of the second example if we add the numbers in the first.

"""

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no need to add this blank line here

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No need to add this blank line.

result = str_pad(self._data, width, side='left', fillchar='0')
return self._wrap_result(result)

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