Merge branch 'master' into PR_TOOL_MERGE_PR_19236

Author: jreback

LICENSES/XARRAY_LICENSE

@@ -0,0 +1,191 @@
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doc/source/api.rst

@@ -2498,6 +2498,20 @@ Scalar introspection
     api.types.is_re_compilable
     api.types.is_scalar
 
+Extensions
+----------
+
+These are primarily intented for library authors looking to extend pandas
+objects.
+
+.. currentmodule:: pandas
+
+.. autosummary::
+   :toctree: generated/
+
+   api.extensions.register_dataframe_accessor
+   api.extensions.register_series_accessor
+   api.extensions.register_index_accessor
 
 .. This is to prevent warnings in the doc build. We don't want to encourage
 .. these methods.

doc/source/developer.rst

@@ -140,3 +140,46 @@ As an example of fully-formed metadata:
          'metadata': None}
     ],
     'pandas_version': '0.20.0'}
+
+.. _developer.register-accessors:
+
+Registering Custom Accessors
+----------------------------
+
+Libraries can use the decorators
+:func:`pandas.api.extensions.register_dataframe_accessor`,
+:func:`pandas.api.extensions.register_series_accessor`, and
+:func:`pandas.api.extensions.register_index_accessor`, to add additional "namespaces" to
+pandas objects. All of these follow a similar convention: you decorate a class, providing the name of attribute to add. The
+class's `__init__` method gets the object being decorated. For example:
+
+.. ipython:: python
+
+   @pd.api.extensions.register_dataframe_accessor("geo")
+   class GeoAccessor(object):
+       def __init__(self, pandas_obj):
+           self._obj = pandas_obj
+
+       @property
+       def center(self):
+           # return the geographic center point of this DataFarme
+           lon = self._obj.latitude
+           lat = self._obj.longitude
+           return (float(lon.mean()), float(lat.mean()))
+
+       def plot(self):
+           # plot this array's data on a map, e.g., using Cartopy
+           pass
+
+Now users can access your methods using the `geo` namespace:
+
+      >>> ds = pd.DataFrame({'longitude': np.linspace(0, 10),
+      ...                    'latitude': np.linspace(0, 20)})
+      >>> ds.geo.center
+      (5.0, 10.0)
+      >>> ds.geo.plot()
+      # plots data on a map
+
+This can be a convenient way to extend pandas objects without subclassing them.
+If you write a custom accessor, make a pull request adding it to our
+:ref:`ecosystem` page.

doc/source/internals.rst

@@ -100,6 +100,8 @@ Subclassing pandas Data Structures
 
   2. Use *composition*. See `here <http://en.wikipedia.org/wiki/Composition_over_inheritance>`_.
 
+  3. Extending by :ref:`registering an accessor <internals.register-accessors>`
+
 This section describes how to subclass ``pandas`` data structures to meet more specific needs. There are 2 points which need attention:
 
 1. Override constructor properties.

doc/source/io.rst

@@ -149,7 +149,7 @@ squeeze : boolean, default ``False``
 prefix : str, default ``None``
   Prefix to add to column numbers when no header, e.g. 'X' for X0, X1, ...
 mangle_dupe_cols : boolean, default ``True``
-  Duplicate columns will be specified as 'X.0'...'X.N', rather than 'X'...'X'.
+  Duplicate columns will be specified as 'X', 'X.1'...'X.N', rather than 'X'...'X'.
   Passing in False will cause data to be overwritten if there are duplicate
   names in the columns.
 
@@ -548,7 +548,7 @@ these names so as to prevent data overwrite:
    pd.read_csv(StringIO(data))
 
 There is no more duplicate data because ``mangle_dupe_cols=True`` by default, which modifies
-a series of duplicate columns 'X'...'X' to become 'X.0'...'X.N'.  If ``mangle_dupe_cols
+a series of duplicate columns 'X'...'X' to become 'X', 'X.1',...'X.N'.  If ``mangle_dupe_cols
 =False``, duplicate data can arise:
 
 .. code-block :: python
@@ -2228,9 +2228,10 @@ round-trippable manner.
    new_df
    new_df.dtypes
 
-Please note that the string `index` is not supported with the round trip
-format, as it is used by default in ``write_json`` to indicate a missing index
-name.
+Please note that the literal string 'index' as the name of an :class:`Index`
+is not round-trippable, nor are any names beginning with 'level_' within a
+:class:`MultiIndex`. These are used by default in :func:`DataFrame.to_json` to
+indicate missing values and the subsequent read cannot distinguish the intent.
 
 .. ipython:: python
 

doc/source/whatsnew/v0.23.0.txt

@@ -202,6 +202,13 @@ Other Enhancements
 - ``Resampler`` objects now have a functioning :attr:`~pandas.core.resample.Resampler.pipe` method.
   Previously, calls to ``pipe`` were diverted to  the ``mean`` method (:issue:`17905`).
 - :func:`~pandas.api.types.is_scalar` now returns ``True`` for ``DateOffset`` objects (:issue:`18943`).
+- Added :func:`pandas.api.extensions.register_dataframe_accessor`,
+  :func:`pandas.api.extensions.register_series_accessor`, and
+  :func:`pandas.api.extensions.register_index_accessor`, accessor for libraries downstream of pandas
+  to register custom accessors like ``.cat`` on pandas objects. See
+  :ref:`Registering Custom Accessors <developer.register-accessors>` for more (:issue:`14781`).
+
+
 - ``IntervalIndex.astype`` now supports conversions between subtypes when passed an ``IntervalDtype`` (:issue:`19197`)
 
 .. _whatsnew_0230.api_breaking:
@@ -225,6 +232,34 @@ If installed, we now require:
    | openpyxl        | 2.4.0           |          |
    +-----------------+-----------------+----------+
 
+.. _whatsnew_0230.api_breaking.deprecate_panel:
+
+Deprecate Panel
+^^^^^^^^^^^^^^^
+
+``Panel`` was deprecated in the 0.20.x release, showing as a ``DeprecationWarning``. Using ``Panel`` will now show a ``FutureWarning``. The recommended way to represent 3-D data are
+with a ``MultiIndex`` on a ``DataFrame`` via the :meth:`~Panel.to_frame` or with the `xarray package <http://xarray.pydata.org/en/stable/>`__. Pandas
+provides a :meth:`~Panel.to_xarray` method to automate this conversion. For more details see :ref:`Deprecate Panel <dsintro.deprecate_panel>` documentation. (:issue:`13563`, :issue:`18324`).
+
+.. ipython:: python
+   :okwarning:
+
+   p = tm.makePanel()
+   p
+
+Convert to a MultiIndex DataFrame
+
+.. ipython:: python
+
+   p.to_frame()
+
+Convert to an xarray DataArray
+
+.. ipython:: python
+   :okwarning:
+
+   p.to_xarray()
+
 
 Build Changes
 ^^^^^^^^^^^^^
@@ -272,6 +307,9 @@ Other API Changes
 - :class:`IntervalIndex` and ``IntervalDtype`` no longer support categorical, object, and string subtypes (:issue:`19016`)
 - The default ``Timedelta`` constructor now accepts an ``ISO 8601 Duration`` string as an argument (:issue:`19040`)
 - ``IntervalDtype`` now returns ``True`` when compared against ``'interval'`` regardless of subtype, and ``IntervalDtype.name`` now returns ``'interval'`` regardless of subtype (:issue:`18980`)
+- :func:`Series.to_csv` now accepts a ``compression`` argument that works in the same way as the ``compression`` argument in :func:`DataFrame.to_csv` (:issue:`18958`)
+- Addition or subtraction of ``NaT`` from :class:`TimedeltaIndex` will return ``TimedeltaIndex`` instead of ``DatetimeIndex`` (:issue:`19124`)
+- :func:`DatetimeIndex.shift` and :func:`TimedeltaIndex.shift` will now raise ``NullFrequencyError`` (which subclasses ``ValueError``, which was raised in older versions) when the index object frequency is ``None`` (:issue:`19147`)
 
 .. _whatsnew_0230.deprecations:
 
@@ -289,6 +327,7 @@ Deprecations
 - :func:`read_excel` has deprecated the ``skip_footer`` parameter. Use ``skipfooter`` instead (:issue:`18836`)
 - The ``is_copy`` attribute is deprecated and will be removed in a future version (:issue:`18801`).
 
+
 .. _whatsnew_0230.prior_deprecations:
 
 Removal of prior version deprecations/changes
@@ -385,10 +424,13 @@ Conversion
 - Bug in :class:`WeekOfMonth` and :class:`LastWeekOfMonth` where default keyword arguments for constructor raised ``ValueError`` (:issue:`19142`)
 - Bug in localization of a naive, datetime string in a ``Series`` constructor with a ``datetime64[ns, tz]`` dtype (:issue:`174151`)
 - :func:`Timestamp.replace` will now handle Daylight Savings transitions gracefully (:issue:`18319`)
+- Bug in :class:`Index` multiplication and division methods where operating with a ``Series`` would return an ``Index`` object instead of a ``Series`` object (:issue:`19042`)
 
 
-
+-
+-
 - Bug in ``.astype()`` to non-ns timedelta units would hold the incorrect dtype (:issue:`19176`, :issue:`19223`, :issue:`12425`)
+- Bug in subtracting :class:`Series` from ``NaT`` incorrectly returning ``NaT`` (:issue:`19158`)
 
 
 Indexing
@@ -453,6 +495,8 @@ Reshaping
 ^^^^^^^^^
 
 - Bug in :func:`DataFrame.stack` which fails trying to sort mixed type levels under Python 3 (:issue:`18310`)
+- Bug in :func:`DataFrame.unstack` which casts int to float if ``columns`` is a ``MultiIndex`` with unused levels (:issue:`17845`)
+- Bug in :func:`DataFrame.unstack` which raises an error if ``index`` is a ``MultiIndex`` with unused labels on the unstacked level (:issue:`18562`)
 - Fixed construction of a :class:`Series` from a ``dict`` containing ``NaN`` as key (:issue:`18480`)
 - Bug in :func:`Series.rank` where ``Series`` containing ``NaT`` modifies the ``Series`` inplace (:issue:`18521`)
 - Bug in :func:`cut` which fails when using readonly arrays (:issue:`18773`)