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# What’s new in 1.0.1 (February 5, 2020)

These are the changes in pandas 1.0.1. See Release notes for a full changelog including other versions of pandas.

## Fixed regressions

- Fixed regression in `DataFrame` setting values with a slice (e.g. `df[-4:] = 1`) indexing by label instead of position (GH 31469)

- Fixed regression when indexing a `Series` or `DataFrame` indexed by `DatetimeIndex` with a slice containing a `datetime.date` (GH 31501)

- Fixed regression in `DataFrame.__setitem__` raising an `AttributeError` with a `MultiIndex` and a non-monotonic indexer (GH 31449)

- Fixed regression in `Series` multiplication when multiplying a numeric `Series` with >10000 elements with a timedelta-like scalar (GH 31457)

- Fixed regression in `.groupby().agg()` raising an `AssertionError` for some reductions like `min` on object-dtype columns (GH 31522)

- Fixed regression in `.groupby()` aggregations with categorical dtype using Cythonized reduction functions (e.g. `first`) (GH 31450)

- Fixed regression in `DataFrameGroupBy.apply()` and `SeriesGroupBy.apply()` if called with a function which returned a non-pandas non-scalar object (e.g. a list or numpy array) (GH 31441)

- Fixed regression in `DataFrame.groupby()` whereby taking the minimum or maximum of a column with period dtype would raise a `TypeError`. (GH 31471)

- Fixed regression in `DataFrame.groupby()` with an empty DataFrame grouping by a level of a MultiIndex (GH 31670).

- Fixed regression in `DataFrame.apply()` with object dtype and non-reducing function (GH 31505)

- Fixed regression in `to_datetime()` when parsing non-nanosecond resolution datetimes (GH 31491)

- Fixed regression in `to_csv()` where specifying an `na_rep` might truncate the values written (GH 31447)

- Fixed regression in `Categorical` construction with `numpy.str_` categories (GH 31499)

- Fixed regression in `DataFrame.loc()` and `DataFrame.iloc()` when selecting a row containing a single `datetime64` or `timedelta64` column (GH 31649)

- Fixed regression where setting `pd.options.display.max_colwidth` was not accepting negative integer. In addition, this behavior has been deprecated in favor of using `None` (GH 31532)

- Fixed regression in objTOJSON.c fix return-type warning (GH 31463)

- Fixed regression in `qcut()` when passed a nullable integer. (GH 31389)

- Fixed regression in assigning to a `Series` using a nullable integer dtype (GH 31446)

- Fixed performance regression when indexing a `DataFrame` or `Series` with a `MultiIndex` for the index using a list of labels (GH 31648)

- Fixed regression in `read_csv()` used in file like object `RawIOBase` is not recognize `encoding` option (GH 31575)

## Deprecations

- Support for negative integer for `pd.options.display.max_colwidth` is deprecated in favor of using `None` (GH 31532)

## Bug fixes

Datetimelike

- Fixed bug in `to_datetime()` raising when `cache=True` and out-of-bound values are present (GH 31491)

Numeric

- Bug in dtypes being lost in `DataFrame.__invert__` (`~` operator) with mixed dtypes (GH 31183) and for extension-array backed `Series` and `DataFrame` (GH 23087)

Plotting

- Plotting tz-aware timeseries no longer gives UserWarning (GH 31205)

Interval

- Bug in `Series.shift()` with `interval` dtype raising a `TypeError` when shifting an interval array of integers or datetimes (GH 34195)

## Contributors

For contributors, please see /usr/share/doc/contributors_list.txt or https://github.com/pandas-dev/pandas/graphs/contributors