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DOC: applied jreback's feedback
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PR #21406
- Applied jreback's feedback in PR #21406
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@deflatSOCO
deflatSOCO committed Sep 25, 2018
1 parent 8bde6c6 commit 74a71fe
Showing 1 changed file with 42 additions and 106 deletions.
148 changes: 42 additions & 106 deletions doc/source/whatsnew/v0.24.0.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -202,49 +202,32 @@ Backwards incompatible API changes
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

:func:`DataFrame.to_csv` now uses :func:`os.linesep` rather than ``'\n'``
for the default line terminator(:issue:`20353`).
- This change only affects when running on Windows, where ``'\r\n'`` was used for line terminator
for the default line terminator (:issue:`20353`).
This change only affects when running on Windows, where ``'\r\n'`` was used for line terminator
even when ``'\n'`` was passed in ``line_terminator``.
- Strictly speeaking, all ``'\n'``s appear in data and line terminator of CSV were converted into ``'\r\n'``s.
- This problem was resolved by passing file object with ``newline='\n'`` option as output, rather than file name.

Previous Behavior on Windows:

.. code-block:: ipython

In [1]: import pandas as pd
In [1]: data = pd.DataFrame({
...: "string_with_lf":["a\nbc"],
...: "string_with_crlf":["a\r\nbc"]
...: })

In [2]: data = pd.DataFrame({
...: "string_with_lf":["abc","d\nef","g\nh\n\ni"],
...: "string_with_crlf":["abc","d\r\nef","g\r\nh\r\n\r\ni"]
...: })
In [2]: data.to_csv("test.csv",index=False,line_terminator='\n')

In [3]: data.to_csv("test.csv",index=False,line_terminator='\n')
In [3]: with open("test.csv", mode='rb') as f:
...: print(f.read())
b'string_with_lf,string_with_crlf\r\n"a\r\nbc","a\r\r\nbc"\r\n'

In [4]: print(pd.read_csv("test.csv"))
string_with_lf string_with_crlf
0 abc abc
1 d\r\nef d\r\r\nef
2 g\r\nh\r\n\r\ni g\r\r\nh\r\r\n\r\r\ni
In [4]: with open("test2.csv", mode='w', newline='\n') as f:
...: data.to_csv(f,index=False,line_terminator='\n')

In [5]: with open("test.csv", mode='rb') as f:
...: print(f.read())
b'string_with_lf,string_with_crlf\r\nabc,abc\r\n"d\r\nef","d\r\r\nef"\r\n"g\r\nh
\r\n\r\ni","g\r\r\nh\r\r\n\r\r\ni"\r\n'
In [5]: with open("test2.csv", mode='rb') as f:
...: print(f.read())
b'string_with_lf,string_with_crlf\n"a\nbc","a\r\nbc"\n'

In [6]: with open("test2.csv", mode='w', newline='\n') as f:
...: data.to_csv(f,index=False,line_terminator='\n')

In [7]: print(pd.read_csv("test2.csv"))
string_with_lf string_with_crlf
0 abc abc
1 d\nef d\r\nef
2 g\nh\n\ni g\r\nh\r\n\r\ni

In [8]: with open("test2.csv", mode='rb') as f:
...: print(f.read())
b'string_with_lf,string_with_crlf\nabc,abc\n"d\nef","d\r\nef"\n"g\nh\n\ni","g\r\
nh\r\n\r\ni"\n'

New Behavior on Windows:

Expand All @@ -254,99 +237,52 @@ New Behavior on Windows:

.. code-block:: ipython

In [1]: import pandas as pd

In [2]: data = pd.DataFrame({
...: "string_with_lf":["abc","d\nef","g\nh\n\ni"],
...: "string_with_crlf":["abc","d\r\nef","g\r\nh\r\n\r\ni"]
...: })
In [1]: data = pd.DataFrame({
...: "string_with_lf":["a\nbc"],
...: "string_with_crlf":["a\r\nbc"]
...: })

In [3]: data.to_csv("test.csv",index=False,line_terminator='\n')
In [2]: data.to_csv("test.csv",index=False,line_terminator='\n')

In [4]: pd.read_csv("test.csv")
Out[4]:
string_with_lf string_with_crlf
0 abc abc
1 d\nef d\r\nef
2 g\nh\n\ni g\r\nh\r\n\r\ni
In [3]: with open("test.csv", mode='rb') as f:
...: print(f.read())
b'string_with_lf,string_with_crlf\n"a\nbc","a\r\nbc"\n'

In [5]: with open("test.csv", mode='rb') as f:
...: binary_str=f.read()
...: binary_str
Out[5]: b'string_with_lf,string_with_crlf\nabc,abc\n"d\nef","d\r\nef"\n"g\nh\n\n
i","g\r\nh\r\n\r\ni"\n'

- On windows, the value of ``os.linesep`` is ``'\r\n'``,
so if ``line_terminator`` is not set, ``'\r\n'`` is used for line terminator.
- Again, it does not affects the value inside the data.

.. code-block:: ipython

In [1]: import pandas as pd
In [1]: data = pd.DataFrame({
...: "string_with_lf":["a\nbc"],
...: "string_with_crlf":["a\r\nbc"]
...: })

In [2]: data = pd.DataFrame({
...: "string_with_lf":["abc","d\nef","g\nh\n\ni"],
...: "string_with_crlf":["abc","d\r\nef","g\r\nh\r\n\r\ni"]
...: })
In [2]: data.to_csv("test.csv",index=False)

In [3]: data.to_csv("test.csv",index=False)
In [3]: with open("test.csv", mode='rb') as f:
...: print(f.read())
b'string_with_lf,string_with_crlf\r\n"a\nbc","a\r\nbc"\r\n'

In [4]: pd.read_csv("test.csv")
Out[4]:
string_with_lf string_with_crlf
0 abc abc
1 d\nef d\r\nef
2 g\nh\n\ni g\r\nh\r\n\r\ni

In [5]: with open("test.csv", mode='rb') as f:
...: binary_str=f.read()
...: binary_str
Out[5]: b'string_with_lf,string_with_crlf\r\nabc,abc\r\n"d\nef","d\r\nef"\r\n"g\
nh\n\ni","g\r\nh\r\n\r\ni"\r\n'

- As default value of ``line_terminator`` changes, just passing file object with ``newline='\n'`` does not set ``'\n'`` to line terminator.
Pass ``line_terminator='\n'`` explicitly.

.. code-block:: ipython

In [1]: import pandas as pd

In [2]: data = pd.DataFrame({
...: "string_with_lf":["abc","d\nef","g\nh\n\ni"],
...: "string_with_crlf":["abc","d\r\nef","g\r\nh\r\n\r\ni"]
...: })

In [3]: with open("test2.csv", mode='w', newline='\n') as f:
...: data.to_csv(f,index=False)

In [4]: pd.read_csv("test2.csv")
Out[4]:
string_with_lf string_with_crlf
0 abc abc
1 d\nef d\r\nef
2 g\nh\n\ni g\r\nh\r\n\r\ni

In [5]: with open("test2.csv", mode='rb') as f:
...: binary_str=f.read()
...: binary_str
Out[5]: b'string_with_lf,string_with_crlf\r\nabc,abc\r\n"d\nef","d\r\nef"\r\n"g\
nh\n\ni","g\r\nh\r\n\r\ni"\r\n'

In [6]: with open("test2.csv", mode='w', newline='\n') as f:
...: data.to_csv(f,index=False,line_terminator='\n')

In [7]: pd.read_csv("test2.csv")
Out[7]:
string_with_lf string_with_crlf
0 abc abc
1 d\nef d\r\nef
2 g\nh\n\ni g\r\nh\r\n\r\ni

In [8]: with open("test2.csv", mode='rb') as f:
...: binary_str=f.read()
...: binary_str
Out[8]: b'string_with_lf,string_with_crlf\nabc,abc\n"d\nef","d\r\nef"\n"g\nh\n\n
i","g\r\nh\r\n\r\ni"\n'
In [1]: data = pd.DataFrame({
...: "string_with_lf":["a\nbc"],
...: "string_with_crlf":["a\r\nbc"]
...: })

In [2]: with open("test2.csv", mode='w', newline='\n') as f:
...: data.to_csv(f,index=False)

In [3]: with open("test2.csv", mode='rb') as f:
...: print(f.read())
b'string_with_lf,string_with_crlf\r\n"a\nbc","a\r\nbc"\r\n'


.. _whatsnew_0240.api_breaking.interval_values:
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