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v0.20.0.txt
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.. _whatsnew_0200:
v0.20.0 (April ??, 2017)
------------------------
This is a major release from 0.19 and includes a small number of API changes, several new features,
enhancements, and performance improvements along with a large number of bug fixes. We recommend that all
users upgrade to this version.
Highlights include:
- The ``.ix`` indexer has been deprecated, see :ref:`here <whatsnew_0200.api_breaking.deprecate_ix>`
- Improved user API when accessing levels in ``.groupby()``, see :ref:`here <whatsnew_0200.enhancements.groupby_access>`
- Improved support for UInt64 dtypes, see :ref:`here <whatsnew_0200.enhancements.uint64_support>`
- Window Binary Corr/Cov operations return a MultiIndex DataFrame rather than a Panel, see :ref:`here <whhatsnew_0200.api_breaking.rolling_pairwise>`
- A new orient for JSON serialization, ``orient='table'``, that uses the Table Schema spec, see :ref:`here <whatsnew_0200.enhancements.table_schema>`
- Support for S3 handling now uses ``s3fs``, see :ref:`here <whatsnew_0200.api_breaking.s3>`
- Google BigQuery support now uses the ``pandas-gbq`` library, see :ref:`here <whatsnew_0200.api_breaking.gbq>`
- Switched the test framework to use `pytest <http://doc.pytest.org/en/latest>`__ (:issue:`13097`)
Check the :ref:`API Changes <whatsnew_0200.api_breaking>` and :ref:`deprecations <whatsnew_0200.deprecations>` before updating.
.. contents:: What's new in v0.20.0
:local:
:backlinks: none
.. _whatsnew_0200.enhancements:
New features
~~~~~~~~~~~~
.. _whatsnew_0200.enhancements.dataio_dtype:
``dtype`` keyword for data IO
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The ``dtype`` keyword argument in the :func:`read_csv` function for specifying the types of parsed columns is now supported with the ``'python'`` engine (:issue:`14295`). See the :ref:`io docs <io.dtypes>` for more information.
.. ipython:: python
:suppress:
from pandas.compat import StringIO
.. ipython:: python
data = "a,b\n1,2\n3,4"
pd.read_csv(StringIO(data), engine='python').dtypes
pd.read_csv(StringIO(data), engine='python', dtype={'a':'float64', 'b':'object'}).dtypes
The ``dtype`` keyword argument is also now supported in the :func:`read_fwf` function for parsing
fixed-width text files, and :func:`read_excel` for parsing Excel files.
.. ipython:: python
data = "a b\n1 2\n3 4"
pd.read_fwf(StringIO(data)).dtypes
pd.read_fwf(StringIO(data), dtype={'a':'float64', 'b':'object'}).dtypes
.. _whatsnew_0120.enhancements.datetime_origin:
``.to_datetime()`` has gained an ``origin`` parameter
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
:func:`to_datetime` has gained a new parameter, ``origin``, to define a reference date
from where to compute the resulting ``DatetimeIndex``. (:issue:`11276`, :issue:`11745`)
Start with 1960-01-01 as the starting date
.. ipython:: python
pd.to_datetime([1, 2, 3], unit='D', origin=pd.Timestamp('1960-01-01'))
The default is set at ``origin='unix'``, which defaults to ``1970-01-01 00:00:00``.
Commonly called 'unix epoch' or POSIX time.
.. ipython:: python
pd.to_datetime([1, 2, 3], unit='D')
.. _whatsnew_0200.enhancements.errors:
pandas errors
^^^^^^^^^^^^^
We are adding a standard public location for all pandas exceptions & warnings ``pandas.errors``. (:issue:`14800`). Previously
these exceptions & warnings could be imported from ``pandas.core.common`` or ``pandas.io.common``. These exceptions and warnings
will be removed from the ``*.common`` locations in a future release. (:issue:`15541`)
The following are now part of this API:
.. code-block:: python
['DtypeWarning',
'EmptyDataError',
'OutOfBoundsDatetime',
'ParserError',
'ParserWarning',
'PerformanceWarning',
'UnsortedIndexError',
'UnsupportedFunctionCall']
.. _whatsnew_0200.enhancements.groupby_access:
Groupby Enhancements
^^^^^^^^^^^^^^^^^^^^
Strings passed to ``DataFrame.groupby()`` as the ``by`` parameter may now reference either column names or index level names (:issue:`5677`)
.. ipython:: python
arrays = [['bar', 'bar', 'baz', 'baz', 'foo', 'foo', 'qux', 'qux'],
['one', 'two', 'one', 'two', 'one', 'two', 'one', 'two']]
index = pd.MultiIndex.from_arrays(arrays, names=['first', 'second'])
df = pd.DataFrame({'A': [1, 1, 1, 1, 2, 2, 3, 3],
'B': np.arange(8)},
index=index)
df
df.groupby(['second', 'A']).sum()
.. _whatsnew_0200.enhancements.compressed_urls:
Better support for compressed URLs in ``read_csv``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The compression code was refactored (:issue:`12688`). As a result, reading
dataframes from URLs in :func:`read_csv` or :func:`read_table` now supports
additional compression methods: ``xz``, ``bz2``, and ``zip`` (:issue:`14570`).
Previously, only ``gzip`` compression was supported. By default, compression of
URLs and paths are now both inferred using their file extensions. Additionally,
support for bz2 compression in the python 2 c-engine improved (:issue:`14874`).
.. ipython:: python
url = 'https://github.com/{repo}/raw/{branch}/{path}'.format(
repo = 'pandas-dev/pandas',
branch = 'master',
path = 'pandas/tests/io/parser/data/salaries.csv.bz2',
)
df = pd.read_table(url, compression='infer') # default, infer compression
df = pd.read_table(url, compression='bz2') # explicitly specify compression
df.head(2)
.. _whatsnew_0200.enhancements.pickle_compression:
Pickle file I/O now supports compression
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
:func:`read_pickle`, :meth:`DataFame.to_pickle` and :meth:`Series.to_pickle`
can now read from and write to compressed pickle files. Compression methods
can be an explicit parameter or be inferred from the file extension.
See :ref:`the docs here <io.pickle.compression>`
.. ipython:: python
df = pd.DataFrame({
'A': np.random.randn(1000),
'B': 'foo',
'C': pd.date_range('20130101', periods=1000, freq='s')})
Using an explicit compression type
.. ipython:: python
df.to_pickle("data.pkl.compress", compression="gzip")
rt = pd.read_pickle("data.pkl.compress", compression="gzip")
rt
Inferring compression type from the extension
.. ipython:: python
df.to_pickle("data.pkl.xz", compression="infer")
rt = pd.read_pickle("data.pkl.xz", compression="infer")
rt
The default is to 'infer
.. ipython:: python
df.to_pickle("data.pkl.gz")
rt = pd.read_pickle("data.pkl.gz")
rt
df["A"].to_pickle("s1.pkl.bz2")
rt = pd.read_pickle("s1.pkl.bz2")
rt
.. ipython:: python
:suppress:
import os
os.remove("data.pkl.compress")
os.remove("data.pkl.xz")
os.remove("data.pkl.gz")
os.remove("s1.pkl.bz2")
.. _whatsnew_0200.enhancements.uint64_support:
UInt64 Support Improved
^^^^^^^^^^^^^^^^^^^^^^^
Pandas has significantly improved support for operations involving unsigned,
or purely non-negative, integers. Previously, handling these integers would
result in improper rounding or data-type casting, leading to incorrect results.
Notably, a new numerical index, ``UInt64Index``, has been created (:issue:`14937`)
.. ipython:: python
idx = pd.UInt64Index([1, 2, 3])
df = pd.DataFrame({'A': ['a', 'b', 'c']}, index=idx)
df.index
- Bug in converting object elements of array-like objects to unsigned 64-bit integers (:issue:`4471`, :issue:`14982`)
- Bug in ``Series.unique()`` in which unsigned 64-bit integers were causing overflow (:issue:`14721`)
- Bug in ``DataFrame`` construction in which unsigned 64-bit integer elements were being converted to objects (:issue:`14881`)
- Bug in ``pd.read_csv()`` in which unsigned 64-bit integer elements were being improperly converted to the wrong data types (:issue:`14983`)
- Bug in ``pd.unique()`` in which unsigned 64-bit integers were causing overflow (:issue:`14915`)
- Bug in ``pd.value_counts()`` in which unsigned 64-bit integers were being erroneously truncated in the output (:issue:`14934`)
.. _whatsnew_0200.enhancements.groupy_categorical:
GroupBy on Categoricals
^^^^^^^^^^^^^^^^^^^^^^^
In previous versions, ``.groupby(..., sort=False)`` would fail with a ``ValueError`` when grouping on a categorical series with some categories not appearing in the data. (:issue:`13179`)
.. ipython:: python
chromosomes = np.r_[np.arange(1, 23).astype(str), ['X', 'Y']]
df = pd.DataFrame({
'A': np.random.randint(100),
'B': np.random.randint(100),
'C': np.random.randint(100),
'chromosomes': pd.Categorical(np.random.choice(chromosomes, 100),
categories=chromosomes,
ordered=True)})
df
Previous Behavior:
.. code-block:: ipython
In [3]: df[df.chromosomes != '1'].groupby('chromosomes', sort=False).sum()
---------------------------------------------------------------------------
ValueError: items in new_categories are not the same as in old categories
New Behavior:
.. ipython:: python
df[df.chromosomes != '1'].groupby('chromosomes', sort=False).sum()
.. _whatsnew_0200.enhancements.table_schema:
Table Schema Output
^^^^^^^^^^^^^^^^^^^
The new orient ``'table'`` for :meth:`DataFrame.to_json`
will generate a `Table Schema`_ compatible string representation of
the data.
.. ipython:: python
df = pd.DataFrame(
{'A': [1, 2, 3],
'B': ['a', 'b', 'c'],
'C': pd.date_range('2016-01-01', freq='d', periods=3),
}, index=pd.Index(range(3), name='idx'))
df
df.to_json(orient='table')
See :ref:`IO: Table Schema for more<io.table_schema>`.
Additionally, the repr for ``DataFrame`` and ``Series`` can now publish
this JSON Table schema representation of the Series or DataFrame if you are
using IPython (or another frontend like `nteract`_ using the Jupyter messaging
protocol).
This gives frontends like the Jupyter notebook and `nteract`_
more flexiblity in how they display pandas objects, since they have
more information about the data.
You must enable this by setting the ``display.html.table_schema`` option to True.
.. _Table Schema: http://specs.frictionlessdata.io/json-table-schema/
.. _nteract: http://nteract.io/
.. _whatsnew_0200.enhancements.scipy_sparse:
SciPy sparse matrix from/to SparseDataFrame
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Pandas now supports creating sparse dataframes directly from ``scipy.sparse.spmatrix`` instances.
See the :ref:`documentation <sparse.scipysparse>` for more information. (:issue:`4343`)
All sparse formats are supported, but matrices that are not in :mod:`COOrdinate <scipy.sparse>` format will be converted, copying data as needed.
.. ipython:: python
from scipy.sparse import csr_matrix
arr = np.random.random(size=(1000, 5))
arr[arr < .9] = 0
sp_arr = csr_matrix(arr)
sp_arr
sdf = pd.SparseDataFrame(sp_arr)
sdf
To convert a ``SparseDataFrame`` back to sparse SciPy matrix in COO format, you can use:
.. ipython:: python
sdf.to_coo()
.. _whatsnew_0200.enhancements.other:
Other Enhancements
^^^^^^^^^^^^^^^^^^
- Integration with the ``feather-format``, including a new top-level ``pd.read_feather()`` and ``DataFrame.to_feather()`` method, see :ref:`here <io.feather>`.
- ``Series.str.replace()`` now accepts a callable, as replacement, which is passed to ``re.sub`` (:issue:`15055`)
- ``Series.str.replace()`` now accepts a compiled regular expression as a pattern (:issue:`15446`)
- ``Series.sort_index`` accepts parameters ``kind`` and ``na_position`` (:issue:`13589`, :issue:`14444`)
- ``DataFrame`` has gained a ``nunique()`` method to count the distinct values over an axis (:issue:`14336`).
- ``DataFrame.groupby()`` has gained a ``.nunique()`` method to count the distinct values for all columns within each group (:issue:`14336`, :issue:`15197`).
- ``pd.read_excel()`` now preserves sheet order when using ``sheetname=None`` (:issue:`9930`)
- Multiple offset aliases with decimal points are now supported (e.g. '0.5min' is parsed as '30s') (:issue:`8419`)
- ``.isnull()`` and ``.notnull()`` have been added to ``Index`` object to make them more consistent with the ``Series`` API (:issue:`15300`)
- New ``UnsortedIndexError`` (subclass of ``KeyError``) raised when indexing/slicing into an
unsorted MultiIndex (:issue:`11897`). This allows differentiation between errors due to lack
of sorting or an incorrect key. See :ref:`here <advanced.unsorted>`
- ``MultiIndex`` has gained a ``.to_frame()`` method to convert to a ``DataFrame`` (:issue:`12397`)
- ``pd.cut`` and ``pd.qcut`` now support datetime64 and timedelta64 dtypes (:issue:`14714`, :issue:`14798`)
- ``pd.qcut`` has gained the ``duplicates='raise'|'drop'`` option to control whether to raise on duplicated edges (:issue:`7751`)
- ``Series`` provides a ``to_excel`` method to output Excel files (:issue:`8825`)
- The ``usecols`` argument in ``pd.read_csv()`` now accepts a callable function as a value (:issue:`14154`)
- The ``skiprows`` argument in ``pd.read_csv()`` now accepts a callable function as a value (:issue:`10882`)
- The ``nrows`` and ``chunksize`` arguments in ``pd.read_csv()`` are supported if both are passed (:issue:`6774`, :issue:`15755`)
- ``pd.DataFrame.plot`` now prints a title above each subplot if ``suplots=True`` and ``title`` is a list of strings (:issue:`14753`)
- ``pd.Series.interpolate`` now supports timedelta as an index type with ``method='time'`` (:issue:`6424`)
- ``Timedelta.isoformat`` method added for formatting Timedeltas as an `ISO 8601 duration`_. See the :ref:`Timedelta docs <timedeltas.isoformat>` (:issue:`15136`)
- ``.select_dtypes()`` now allows the string 'datetimetz' to generically select datetimes with tz (:issue:`14910`)
- The ``.to_latex()`` method will now accept ``multicolumn`` and ``multirow`` arguments to use the accompanying LaTeX enhancements
- ``pd.merge_asof()`` gained the option ``direction='backward'|'forward'|'nearest'`` (:issue:`14887`)
- ``Series/DataFrame.asfreq()`` have gained a ``fill_value`` parameter, to fill missing values (:issue:`3715`).
- ``Series/DataFrame.resample.asfreq`` have gained a ``fill_value`` parameter, to fill missing values during resampling (:issue:`3715`).
- ``pandas.tools.hashing`` has gained a ``hash_tuples`` routine, and ``hash_pandas_object`` has gained the ability to hash a ``MultiIndex`` (:issue:`15224`)
- ``Series/DataFrame.squeeze()`` have gained the ``axis`` parameter. (:issue:`15339`)
- ``DataFrame.to_excel()`` has a new ``freeze_panes`` parameter to turn on Freeze Panes when exporting to Excel (:issue:`15160`)
- ``pd.read_html()`` will parse multiple header rows, creating a multiindex header. (:issue:`13434`).
- HTML table output skips ``colspan`` or ``rowspan`` attribute if equal to 1. (:issue:`15403`)
- ``pd.TimedeltaIndex`` now has a custom datetick formatter specifically designed for nanosecond level precision (:issue:`8711`)
- ``pd.types.concat.union_categoricals`` gained the ``ignore_ordered`` argument to allow ignoring the ordered attribute of unioned categoricals (:issue:`13410`). See the :ref:`categorical union docs <categorical.union>` for more information.
- ``pd.DataFrame.to_latex`` and ``pd.DataFrame.to_string`` now allow optional header aliases. (:issue:`15536`)
- Re-enable the ``parse_dates`` keyword of ``read_excel`` to parse string columns as dates (:issue:`14326`)
- Added ``.empty`` property to subclasses of ``Index``. (:issue:`15270`)
- Enabled floor division for ``Timedelta`` and ``TimedeltaIndex`` (:issue:`15828`)
- ``pandas.io.json.json_normalize()`` gained the option ``errors='ignore'|'raise'``; the default is ``errors='raise'`` which is backward compatible. (:issue:`14583`)
- ``pandas.io.json.json_normalize()`` with an empty ``list`` will return an empty ``DataFrame`` (:issue:`15534`)
- ``pandas.io.json.json_normalize()`` has gained a ``sep`` option that accepts ``str`` to separate joined fields; the default is ".", which is backward compatible. (:issue:`14883`)
.. _ISO 8601 duration: https://en.wikipedia.org/wiki/ISO_8601#Durations
.. _whatsnew_0200.api_breaking:
Backwards incompatible API changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. _whatsnew_0200.api_breaking.deprecate_ix:
Deprecate .ix
^^^^^^^^^^^^^
The ``.ix`` indexer is deprecated, in favor of the more strict ``.iloc`` and ``.loc`` indexers. ``.ix`` offers a lot of magic on the inference of what the user wants to do. To wit, ``.ix`` can decide to index *positionally* OR via *labels*, depending on the data type of the index. This has caused quite a bit of user confusion over the years. The full indexing documentation are :ref:`here <indexing>`. (:issue:`14218`)
The recommended methods of indexing are:
- ``.loc`` if you want to *label* index
- ``.iloc`` if you want to *positionally* index.
Using ``.ix`` will now show a ``DeprecationWarning`` with a link to some examples of how to convert code :ref:`here <indexing.deprecate_ix>`.
.. ipython:: python
df = pd.DataFrame({'A': [1, 2, 3],
'B': [4, 5, 6]},
index=list('abc'))
df
Previous Behavior, where you wish to get the 0th and the 2nd elements from the index in the 'A' column.
.. code-block:: ipython
In [3]: df.ix[[0, 2], 'A']
Out[3]:
a 1
c 3
Name: A, dtype: int64
Using ``.loc``. Here we will select the appropriate indexes from the index, then use *label* indexing.
.. ipython:: python
df.loc[df.index[[0, 2]], 'A']
Using ``.iloc``. Here we will get the location of the 'A' column, then use *positional* indexing to select things.
.. ipython:: python
df.iloc[[0, 2], df.columns.get_loc('A')]
.. _whatsnew.api_breaking.io_compat:
Possible incompat for HDF5 formats for pandas < 0.13.0
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
``pd.TimeSeries`` was deprecated officially in 0.17.0, though has only been an alias since 0.13.0. It has
been dropped in favor of ``pd.Series``. (:issue:`15098`).
This *may* cause HDF5 files that were created in prior versions to become unreadable if ``pd.TimeSeries``
was used. This is most likely to be for pandas < 0.13.0. If you find yourself in this situation.
You can use a recent prior version of pandas to read in your HDF5 files,
then write them out again after applying the procedure below.
.. code-block:: ipython
In [2]: s = pd.TimeSeries([1,2,3], index=pd.date_range('20130101', periods=3))
In [3]: s
Out[3]:
2013-01-01 1
2013-01-02 2
2013-01-03 3
Freq: D, dtype: int64
In [4]: type(s)
Out[4]: pandas.core.series.TimeSeries
In [5]: s = pd.Series(s)
In [6]: s
Out[6]:
2013-01-01 1
2013-01-02 2
2013-01-03 3
Freq: D, dtype: int64
In [7]: type(s)
Out[7]: pandas.core.series.Series
.. _whatsnew_0200.api_breaking.index_map:
Map on Index types now return other Index types
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
``map`` on an ``Index`` now returns an ``Index``, not a numpy array (:issue:`12766`)
.. ipython:: python
idx = Index([1, 2])
idx
mi = MultiIndex.from_tuples([(1, 2), (2, 4)])
mi
Previous Behavior:
.. code-block:: ipython
In [5]: idx.map(lambda x: x * 2)
Out[5]: array([2, 4])
In [6]: idx.map(lambda x: (x, x * 2))
Out[6]: array([(1, 2), (2, 4)], dtype=object)
In [7]: mi.map(lambda x: x)
Out[7]: array([(1, 2), (2, 4)], dtype=object)
In [8]: mi.map(lambda x: x[0])
Out[8]: array([1, 2])
New Behavior:
.. ipython:: python
idx.map(lambda x: x * 2)
idx.map(lambda x: (x, x * 2))
mi.map(lambda x: x)
mi.map(lambda x: x[0])
``map`` on a ``Series`` with ``datetime64`` values may return ``int64`` dtypes rather than ``int32``
.. ipython:: python
s = Series(date_range('2011-01-02T00:00', '2011-01-02T02:00', freq='H').tz_localize('Asia/Tokyo'))
s
Previous Behavior:
.. code-block:: ipython
In [9]: s.map(lambda x: x.hour)
Out[9]:
0 0
1 1
2 2
dtype: int32
New Behavior:
.. ipython:: python
s.map(lambda x: x.hour)
.. _whatsnew_0200.api_breaking.index_dt_field:
Accessing datetime fields of Index now return Index
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The datetime-related attributes (see :ref:`here <timeseries.components>`
for an overview) of ``DatetimeIndex``, ``PeriodIndex`` and ``TimedeltaIndex`` previously
returned numpy arrays. They will now return a new ``Index`` object, except
in the case of a boolean field, where the result will stil be a boolean ndarray. (:issue:`15022`)
Previous behaviour:
.. code-block:: ipython
In [1]: idx = pd.date_range("2015-01-01", periods=5, freq='10H')
In [2]: idx.hour
Out[2]: array([ 0, 10, 20, 6, 16], dtype=int32)
New Behavior:
.. ipython:: python
idx = pd.date_range("2015-01-01", periods=5, freq='10H')
idx.hour
This has the advantage that specific ``Index`` methods are still available on the
result. On the other hand, this might have backward incompatibilities: e.g.
compared to numpy arrays, ``Index`` objects are not mutable. To get the original
ndarray, you can always convert explicitly using ``np.asarray(idx.hour)``.
.. _whatsnew_0200.api_breaking.s3:
S3 File Handling
^^^^^^^^^^^^^^^^
pandas now uses `s3fs <http://s3fs.readthedocs.io/>`_ for handling S3 connections. This shouldn't break
any code. However, since ``s3fs`` is not a required dependency, you will need to install it separately, like ``boto``
in prior versions of pandas. (:issue:`11915`).
.. _whatsnew_0200.api_breaking.partial_string_indexing:
Partial String Indexing Changes
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
:ref:`DatetimeIndex Partial String Indexing <timeseries.partialindexing>` now works as exact match, provided that string resolution coincides with index resolution, including a case when both are seconds (:issue:`14826`). See :ref:`Slice vs. Exact Match <timeseries.slice_vs_exact_match>` for details.
.. ipython:: python
df = DataFrame({'a': [1, 2, 3]}, DatetimeIndex(['2011-12-31 23:59:59',
'2012-01-01 00:00:00',
'2012-01-01 00:00:01']))
Previous Behavior:
.. code-block:: ipython
In [4]: df['2011-12-31 23:59:59']
Out[4]:
a
2011-12-31 23:59:59 1
In [5]: df['a']['2011-12-31 23:59:59']
Out[5]:
2011-12-31 23:59:59 1
Name: a, dtype: int64
New Behavior:
.. code-block:: ipython
In [4]: df['2011-12-31 23:59:59']
KeyError: '2011-12-31 23:59:59'
In [5]: df['a']['2011-12-31 23:59:59']
Out[5]: 1
.. _whatsnew_0200.api_breaking.concat_dtypes:
Concat of different float dtypes will not automatically upcast
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Previously, ``concat`` of multiple objects with different ``float`` dtypes would automatically upcast results to a dtype of ``float64``.
Now the smallest acceptable dtype will be used (:issue:`13247`)
.. ipython:: python
df1 = pd.DataFrame(np.array([1.0], dtype=np.float32, ndmin=2))
df1.dtypes
.. ipython:: python
df2 = pd.DataFrame(np.array([np.nan], dtype=np.float32, ndmin=2))
df2.dtypes
Previous Behavior:
.. code-block:: ipython
In [7]: pd.concat([df1,df2]).dtypes
Out[7]:
0 float64
dtype: object
New Behavior:
.. ipython:: python
pd.concat([df1,df2]).dtypes
.. _whatsnew_0200.api_breaking.gbq:
Pandas Google BigQuery support has moved
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pandas has split off Google BigQuery support into a separate package ``pandas-gbq``. You can ``pip install pandas-gbq`` to get it.
The functionality of :func:`read_gbq` and :meth:`DataFrame.to_gbq` remain the same with the currently released version of ``pandas-gbq=0.1.3``.
Documentation is now hosted `here <https://pandas-gbq.readthedocs.io/>`__ (:issue:`15347`)
.. _whatsnew_0200.api_breaking.memory_usage:
Memory Usage for Index is more Accurate
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In previous versions, showing ``.memory_usage()`` on a pandas structure that has an index, would only include actual index values and not include structures that facilitated fast indexing. This will generally be different for ``Index`` and ``MultiIndex`` and less-so for other index types. (:issue:`15237`)
Previous Behavior:
.. code-block:: ipython
In [8]: index = Index(['foo', 'bar', 'baz'])
In [9]: index.memory_usage(deep=True)
Out[9]: 180
In [10]: index.get_loc('foo')
Out[10]: 0
In [11]: index.memory_usage(deep=True)
Out[11]: 180
New Behavior:
.. code-block:: ipython
In [8]: index = Index(['foo', 'bar', 'baz'])
In [9]: index.memory_usage(deep=True)
Out[9]: 180
In [10]: index.get_loc('foo')
Out[10]: 0
In [11]: index.memory_usage(deep=True)
Out[11]: 260
.. _whatsnew_0200.api_breaking.extensions:
Extension Modules Moved
^^^^^^^^^^^^^^^^^^^^^^^
Some formerly public c/c++/cython extension modules have been moved and/or renamed. These are all removed from the public API.
If indicated, a deprecation warning will be issued if you reference that module. (:issue:`12588`)
.. csv-table::
:header: "Previous Location", "New Location", "Deprecated"
:widths: 30, 30, 4
"pandas.lib", "pandas._libs.lib", "X"
"pandas.tslib", "pandas._libs.tslib", "X"
"pandas._join", "pandas._libs.join", ""
"pandas._period", "pandas._libs.period", ""
"pandas.msgpack", "pandas.io.msgpack", ""
"pandas.index", "pandas._libs.index", ""
"pandas.algos", "pandas._libs.algos", ""
"pandas.hashtable", "pandas._libs.hashtable", ""
"pandas.json", "pandas.io.json.libjson", "X"
"pandas.parser", "pandas.io.libparsers", "X"
"pandas.io.sas.saslib", "pandas.io.sas.libsas", ""
"pandas._testing", "pandas.util.libtesting", ""
"pandas._sparse", "pandas.sparse.libsparse", ""
"pandas._hash", "pandas.tools.libhash", ""
"pandas._window", "pandas.core.libwindow", ""
.. _whatsnew_0200.api_breaking.groupby_describe:
Groupby Describe Formatting
^^^^^^^^^^^^^^^^^^^^^^^^^^^
The output formatting of ``groupby.describe()`` now labels the ``describe()`` metrics in the columns instead of the index.
This format is consistent with ``groupby.agg()`` when applying multiple functions at once. (:issue:`4792`)
Previous Behavior:
.. code-block:: ipython
In [1]: df = pd.DataFrame({'A': [1, 1, 2, 2], 'B': [1, 2, 3, 4]})
In [2]: df.groupby('A').describe()
Out[2]:
B
A
1 count 2.000000
mean 1.500000
std 0.707107
min 1.000000
25% 1.250000
50% 1.500000
75% 1.750000
max 2.000000
2 count 2.000000
mean 3.500000
std 0.707107
min 3.000000
25% 3.250000
50% 3.500000
75% 3.750000
max 4.000000
In [3]: df.groupby('A').agg([np.mean, np.std, np.min, np.max])
Out[3]:
B
mean std amin amax
A
1 1.5 0.707107 1 2
2 3.5 0.707107 3 4
New Behavior:
.. ipython:: python
df = pd.DataFrame({'A': [1, 1, 2, 2], 'B': [1, 2, 3, 4]})
df.groupby('A').describe()
df.groupby('A').agg([np.mean, np.std, np.min, np.max])
.. _whatsnew_0200.api_breaking.rolling_pairwise:
Window Binary Corr/Cov operations return a MultiIndex DataFrame
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
A binary window operation, like ``.corr()`` or ``.cov()``, when operating on a ``.rolling(..)``, ``.expanding(..)``, or ``.ewm(..)`` object,
will now return a 2-level ``MultiIndexed DataFrame`` rather than a ``Panel``. These are equivalent in function,
but MultiIndexed DataFrames enjoy more support in pandas.
See the section on :ref:`Windowed Binary Operations <stats.moments.binary>` for more information. (:issue:`15677`)
.. ipython:: python
np.random.seed(1234)
df = pd.DataFrame(np.random.rand(100, 2),
columns=pd.Index(['A', 'B'], name='bar'),
index=pd.date_range('20160101',
periods=100, freq='D', name='foo'))
df
Old Behavior:
.. code-block:: ipython
In [2]: df.rolling(12).corr()
Out[2]:
<class 'pandas.core.panel.Panel'>
Dimensions: 100 (items) x 2 (major_axis) x 2 (minor_axis)
Items axis: 2016-01-01 00:00:00 to 2016-04-09 00:00:00
Major_axis axis: A to B
Minor_axis axis: A to B
New Behavior:
.. ipython:: python
res = df.rolling(12).corr()
res
Retrieving a correlation matrix for a cross-section
.. ipython:: python
df.rolling(12).corr().loc['2016-04-07']
.. _whatsnew_0200.api_breaking.hdfstore_where:
HDFStore where string comparison
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In previous versions most types could be compared to string column in a ``HDFStore``
usually resulting in an invalid comparsion. These comparisions will now raise a
``TypeError`` (:issue:`15492`)
New Behavior:
.. code-block:: ipython
In [15]: df = pd.DataFrame({'unparsed_date': ['2014-01-01', '2014-01-01']})
In [16]: df.dtypes
Out[16]:
unparsed_date object
dtype: object
In [17]: df.to_hdf('store.h5', 'key', format='table', data_columns=True)
In [18]: ts = pd.Timestamp('2014-01-01')
In [19]: pd.read_hdf('store.h5', 'key', where='unparsed_date > ts')
TypeError: Cannot compare 2014-01-01 00:00:00 of
type <class 'pandas.tslib.Timestamp'> to string column
.. _whatsnew_0200.api_breaking.index_order:
Index.intersection and inner join now preserve the order of the left Index
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
:meth:`Index.intersection` now preserves the order of the calling ``Index`` (left)
instead of the other ``Index`` (right) (:issue:`15582`). This affects the inner
joins, :meth:`DataFrame.join` and :func:`merge`, and the ``.align`` methods.
- ``Index.intersection``
.. ipython:: python
left = pd.Index([2, 1, 0])
left
right = pd.Index([1, 2, 3])
right
Previous Behavior:
.. code-block:: ipython
In [4]: left.intersection(right)
Out[4]: Int64Index([1, 2], dtype='int64')
New Behavior:
.. ipython:: python
left.intersection(right)
- ``DataFrame.join`` and ``pd.merge``
.. ipython:: python
left = pd.DataFrame({'a': [20, 10, 0]}, index=[2, 1, 0])
left
right = pd.DataFrame({'b': [100, 200, 300]}, index=[1, 2, 3])
right
Previous Behavior:
.. code-block:: ipython
In [4]: left.join(right, how='inner')
Out[4]:
a b
1 10 100
2 20 200
New Behavior:
.. ipython:: python
left.join(right, how='inner')
.. _whatsnew_0200.api:
Other API Changes
^^^^^^^^^^^^^^^^^
- ``numexpr`` version is now required to be >= 2.4.6 and it will not be used at all if this requisite is not fulfilled (:issue:`15213`).
- ``CParserError`` has been renamed to ``ParserError`` in ``pd.read_csv()`` and will be removed in the future (:issue:`12665`)
- ``SparseArray.cumsum()`` and ``SparseSeries.cumsum()`` will now always return ``SparseArray`` and ``SparseSeries`` respectively (:issue:`12855`)
- ``DataFrame.applymap()`` with an empty ``DataFrame`` will return a copy of the empty ``DataFrame`` instead of a ``Series`` (:issue:`8222`)
- ``.loc`` has compat with ``.ix`` for accepting iterators, and NamedTuples (:issue:`15120`)
- ``interpolate()`` and ``fillna()`` will raise a ``ValueError`` if the ``limit`` keyword argument is not greater than 0. (:issue:`9217`)
- ``pd.read_csv()`` will now issue a ``ParserWarning`` whenever there are conflicting values provided by the ``dialect`` parameter and the user (:issue:`14898`)
- ``pd.read_csv()`` will now raise a ``ValueError`` for the C engine if the quote character is larger than than one byte (:issue:`11592`)
- ``inplace`` arguments now require a boolean value, else a ``ValueError`` is thrown (:issue:`14189`)
- ``pandas.api.types.is_datetime64_ns_dtype`` will now report ``True`` on a tz-aware dtype, similar to ``pandas.api.types.is_datetime64_any_dtype``
- ``DataFrame.asof()`` will return a null filled ``Series`` instead the scalar ``NaN`` if a match is not found (:issue:`15118`)
- Specific support for ``copy.copy()`` and ``copy.deepcopy()`` functions on NDFrame objects (:issue:`15444`)
- ``Series.sort_values()`` accepts a one element list of bool for consistency with the behavior of ``DataFrame.sort_values()`` (:issue:`15604`)
- ``.merge()`` and ``.join()`` on ``category`` dtype columns will now preserve the category dtype when possible (:issue:`10409`)
- ``SparseDataFrame.default_fill_value`` will be 0, previously was ``nan`` in the return from ``pd.get_dummies(..., sparse=True)`` (:issue:`15594`)
- The default behaviour of ``Series.str.match`` has changed from extracting
groups to matching the pattern. The extracting behaviour was deprecated
since pandas version 0.13.0 and can be done with the ``Series.str.extract``
method (:issue:`5224`). As a consequence, the ``as_indexer`` keyword is
ignored (no longer needed to specify the new behaviour) and is deprecated.
- ``NaT`` will now correctly report ``False`` for datetimelike boolean operations such as ``is_month_start`` (:issue:`15781`)
- ``NaT`` will now correctly return ``np.nan`` for ``Timedelta`` and ``Period`` accessors such as ``days`` and ``quarter`` (:issue:`15782`)
- ``NaT`` will now returns ``NaT`` for ``tz_localize`` and ``tz_convert``
methods (:issue:`15830`)
- ``DataFrame`` and ``Panel`` constructors with invalid input will now raise ``ValueError`` rather than ``PandasError``, if called with scalar inputs and not axes (:issue:`15541`)
- ``DataFrame`` and ``Panel`` constructors with invalid input will now raise ``ValueError`` rather than ``pandas.core.common.PandasError``, if called with scalar inputs and not axes; The exception ``PandasError`` is removed as well. (:issue:`15541`)
- The exception ``pandas.core.common.AmbiguousIndexError`` is removed as it is not referenced (:issue:`15541`)
.. _whatsnew_0200.develop:
Development Changes
~~~~~~~~~~~~~~~~~~~
- Building pandas for development now requires ``cython >= 0.23`` (:issue:`14831`)
- Require at least 0.23 version of cython to avoid problems with character encodings (:issue:`14699`)
- Reorganization of timeseries tests (:issue:`14854`)
- Reorganization of date converter tests (:issue:`15707`)
.. _whatsnew_0200.deprecations:
Deprecations
~~~~~~~~~~~~
- ``SparseArray.to_dense()`` has deprecated the ``fill`` parameter, as that parameter was not being respected (:issue:`14647`)
- ``SparseSeries.to_dense()`` has deprecated the ``sparse_only`` parameter (:issue:`14647`)
- ``Series.repeat()`` has deprecated the ``reps`` parameter in favor of ``repeats`` (:issue:`12662`)
- ``Index.repeat()`` and ``MultiIndex.repeat()`` have deprecated the ``n`` parameter in favor of ``repeats`` (:issue:`12662`)
- ``Categorical.searchsorted()`` and ``Series.searchsorted()`` have deprecated the ``v`` parameter in favor of ``value`` (:issue:`12662`)
- ``TimedeltaIndex.searchsorted()``, ``DatetimeIndex.searchsorted()``, and ``PeriodIndex.searchsorted()`` have deprecated the ``key`` parameter in favor of ``value`` (:issue:`12662`)
- ``DataFrame.astype()`` has deprecated the ``raise_on_error`` parameter in favor of ``errors`` (:issue:`14878`)
- ``Series.sortlevel`` and ``DataFrame.sortlevel`` have been deprecated in favor of ``Series.sort_index`` and ``DataFrame.sort_index`` (:issue:`15099`)
- importing ``concat`` from ``pandas.tools.merge`` has been deprecated in favor of imports from the ``pandas`` namespace. This should only affect explict imports (:issue:`15358`)
- ``Series/DataFrame/Panel.consolidate()`` been deprecated as a public method. (:issue:`15483`)
- The ``as_indexer`` keyword of ``Series.str.match()`` has been deprecated (ignored keyword) (:issue:`15257`).
- The following top-level pandas functions have been deprecated and will be removed in a future version (:issue:`13790`)
* ``pd.pnow()``, replaced by ``Period.now()``
* ``pd.Term``, is removed, as it is not applicable to user code. Instead use in-line string expressions in the where clause when searching in HDFStore
* ``pd.Expr``, is removed, as it is not applicable to user code.
* ``pd.match()``, is removed.
* ``pd.groupby()``, replaced by using the ``.groupby()`` method directly on a ``Series/DataFrame``
.. _whatsnew_0200.prior_deprecations:
Removal of prior version deprecations/changes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- The ``pandas.rpy`` module is removed. Similar functionality can be accessed
through the `rpy2 <https://rpy2.readthedocs.io/>`__ project.
See the :ref:`R interfacing docs <rpy>` for more details.
- The ``pandas.io.ga`` module with a ``google-analytics`` interface is removed (:issue:`11308`).
Similar functionality can be found in the `Google2Pandas <https://github.com/panalysis/Google2Pandas>`__ package.
- ``pd.to_datetime`` and ``pd.to_timedelta`` have dropped the ``coerce`` parameter in favor of ``errors`` (:issue:`13602`)
- ``pandas.stats.fama_macbeth``, ``pandas.stats.ols``, ``pandas.stats.plm`` and ``pandas.stats.var``, as well as the top-level ``pandas.fama_macbeth`` and ``pandas.ols`` routines are removed. Similar functionaility can be found in the `statsmodels <shttp://www.statsmodels.org/dev/>`__ package. (:issue:`11898`)
- The ``TimeSeries`` and ``SparseTimeSeries`` classes, aliases of ``Series``
and ``SparseSeries``, are removed (:issue:`10890`, :issue:`15098`).
- ``Series.is_time_series`` is dropped in favor of ``Series.index.is_all_dates`` (:issue:`15098`)
- The deprecated ``irow``, ``icol``, ``iget`` and ``iget_value`` methods are removed
in favor of ``iloc`` and ``iat`` as explained :ref:`here <whatsnew_0170.deprecations>` (:issue:`10711`).
- The deprecated ``DataFrame.iterkv()`` has been removed in favor of ``DataFrame.iteritems()`` (:issue:`10711`)
- The ``Categorical`` constructor has dropped the ``name`` parameter (:issue:`10632`)
- ``Categorical`` has dropped support for ``NaN`` categories (:issue:`10748`)
- The ``take_last`` parameter has been dropped from ``duplicated()``, ``drop_duplicates()``, ``nlargest()``, and ``nsmallest()`` methods (:issue:`10236`, :issue:`10792`, :issue:`10920`)
- ``Series``, ``Index``, and ``DataFrame`` have dropped the ``sort`` and ``order`` methods (:issue:`10726`)
- Where clauses in ``pytables`` are only accepted as strings and expressions types and not other data-types (:issue:`12027`)
- ``DataFrame`` has dropped the ``combineAdd`` and ``combineMult`` methods in favor of ``add`` and ``mul`` respectively (:issue:`10735`)
.. _whatsnew_0200.performance:
Performance Improvements
~~~~~~~~~~~~~~~~~~~~~~~~
- Improved performance of ``pd.wide_to_long()`` (:issue:`14779`)
- Improved performance of ``pd.factorize()`` by releasing the GIL with ``object`` dtype when inferred as strings (:issue:`14859`)
- Improved performance of timeseries plotting with an irregular DatetimeIndex