v1.1.0.rst

What's new in 1.1.0 (??)

These are the changes in pandas 1.1.0. See :ref:`release` for a full changelog including other versions of pandas.

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Enhancements

Nonmonotonic PeriodIndex Partial String Slicing

:class:`PeriodIndex` now supports partial string slicing for non-monotonic indexes, mirroring :class:`DatetimeIndex` behavior (:issue:`31096`)

For example:

.. ipython:: python

   dti = pd.date_range("2014-01-01", periods=30, freq="30D")
   pi = dti.to_period("D")
   ser_monotonic = pd.Series(np.arange(30), index=pi)
   shuffler = list(range(0, 30, 2)) + list(range(1, 31, 2))
   ser = ser_monotonic[shuffler]
   ser

.. ipython:: python

   ser["2014"]
   ser.loc["May 2015"]

Indexing with Nullable Boolean Arrays

Previously indexing with a nullable Boolean array would raise a ValueError, however this is now permitted with NA being treated as False. (:issue:`31503`)

Other enhancements

• :class:`Styler` may now render CSS more efficiently where multiple cells have the same styling (:issue:`30876`)

Other API changes

• :meth:`Series.describe` will now show distribution percentiles for datetime dtypes, statistics first and last will now be min and max to match with numeric dtypes in :meth:`DataFrame.describe` (:issue:`30164`)
• :meth:`Groupby.groups` now returns an abbreviated representation when called on large dataframes (:issue:`1135`)

Backwards incompatible API changes

• :meth:`DataFrame.swaplevels` now raises a TypeError if the axis is not a :class:`MultiIndex`. Previously a AttributeError was raised (:issue:`31126`)
• :meth:`DataFrameGroupby.mean` and :meth:`SeriesGroupby.mean` (and similarly for :meth:`~DataFrameGroupby.median`, :meth:`~DataFrameGroupby.std`` and :meth:`~DataFrameGroupby.var``) now raise a TypeError if a not-accepted keyword argument is passed into it. Previously a UnsupportedFunctionCall was raised (AssertionError if min_count passed into :meth:`~DataFrameGroupby.median``) (:issue:`31485`)

Deprecations

Performance improvements

• Performance improvement in :class:`Timedelta` constructor (:issue:`30543`)
• Performance improvement in :class:`Timestamp` constructor (:issue:`30543`)

Bug fixes

Categorical

Datetimelike

• Bug in :class:`Timestamp` where constructing :class:`Timestamp` from ambiguous epoch time and calling constructor again changed :meth:`Timestamp.value` property (:issue:`24329`)
• :meth:`DatetimeArray.searchsorted`, :meth:`TimedeltaArray.searchsorted`, :meth:`PeriodArray.searchsorted` not recognizing non-pandas scalars and incorrectly raising ValueError instead of TypeError (:issue:`30950`)
• Bug in :class:`Timestamp` where constructing :class:`Timestamp` with dateutil timezone less than 128 nanoseconds before daylight saving time switch from winter to summer would result in nonexistent time (:issue:`31043`)

Timedelta

• Bug in constructing a :class:`Timedelta` with a high precision integer that would round the :class:`Timedelta` components (:issue:`31354`)

Timezones

Numeric

• Bug in :meth:`DataFrame.floordiv` with axis=0 not treating division-by-zero like :meth:`Series.floordiv` (:issue:`31271`)

Conversion

• Bug in :class:`Series` construction from NumPy array with big-endian datetime64 dtype (:issue:`29684`)

Strings

Interval

Indexing

• Bug in slicing on a :class:`DatetimeIndex` with a partial-timestamp dropping high-resolution indices near the end of a year, quarter, or month (:issue:`31064`)
• Bug in :meth:`PeriodIndex.get_loc` treating higher-resolution strings differently from :meth:`PeriodIndex.get_value` (:issue:`31172`)
• Bug in :meth:`Series.at` and :meth:`DataFrame.at` not matching .loc behavior when looking up an integer in a :class:`Float64Index` (:issue:`31329`)
• Bug in :meth:`PeriodIndex.is_monotonic` incorrectly returning True when containing leading NaT entries (:issue:`31437`)
• Bug in :meth:`DatetimeIndex.get_loc` raising KeyError with converted-integer key instead of the user-passed key (:issue:`31425`)

Missing

MultiIndex

• Bug in :meth:`Dataframe.loc` when used with a :class:`MultiIndex`. The returned values were not in the same order as the given inputs (:issue:`22797`)

.. ipython:: python

        df = pd.DataFrame(np.arange(4),
                          index=[["a", "a", "b", "b"], [1, 2, 1, 2]])
        # Rows are now ordered as the requested keys
        df.loc[(['b', 'a'], [2, 1]), :]

I/O

• Bug in :meth:`read_json` where integer overflow was occuring when json contains big number strings. (:issue:`30320`)
• Bug in :meth:`DataFrame.to_json` was raising NotFoundError when path_or_buf was an S3 URI (:issue:`28375`)

Plotting

• :func:`.plot` for line/bar now accepts color by dictonary (:issue:`8193`).

Groupby/resample/rolling

• Bug in :meth:`GroupBy.apply` raises ValueError when the by axis is not sorted and has duplicates and the applied func does not mutate passed in objects (:issue:`30667`)
• Bug in :meth:`DataFrameGroupby.transform` produces incorrect result with transformation functions (:issue:`30918`)

Reshaping

• Bug effecting all numeric and boolean reduction methods not returning subclassed data type. (:issue:`25596`)
• Bug in :meth:`DataFrame.pivot_table` when only MultiIndexed columns is set (:issue:`17038`)
• Bug in :meth:`DataFrame.unstack` and :meth:`Series.unstack` can take tuple names in MultiIndexed data (:issue:`19966`)
• Bug in :meth:`DataFrame.pivot_table` when margin is True and only column is defined (:issue:`31016`)
• Fix incorrect error message in :meth:`DataFrame.pivot` when columns is set to None. (:issue:`30924`)
• Bug in :func:`crosstab` when inputs are two Series and have tuple names, the output will keep dummy MultiIndex as columns. (:issue:`18321`)
• Bug in :func:`concat` where the resulting indices are not copied when copy=True (:issue:`29879`)

Sparse

ExtensionArray

Other

• Appending a dictionary to a :class:`DataFrame` without passing ignore_index=True will raise TypeError: Can only append a dict if ignore_index=True instead of TypeError: Can only append a Series if ignore_index=True or if the Series has a name (:issue:`30871`)
• Set operations on an object-dtype :class:`Index` now always return object-dtype results (:issue:`31401`)

Contributors