# What’s new in 1.1.1 (August 20, 2020)#

These are the changes in pandas 1.1.1. See Release notes for a full changelog including other versions of pandas.

## Fixed regressions#

Fixed regression in

`CategoricalIndex.format()`

where, when stringified scalars had different lengths, the shorter string would be right-filled with spaces, so it had the same length as the longest string (GH 35439)Fixed regression in

`Series.truncate()`

when trying to truncate a single-element series (GH 35544)Fixed regression where

`DataFrame.to_numpy()`

would raise a`RuntimeError`

for mixed dtypes when converting to`str`

(GH 35455)Fixed regression where

`read_csv()`

would raise a`ValueError`

when`pandas.options.mode.use_inf_as_na`

was set to`True`

(GH 35493)Fixed regression where

`pandas.testing.assert_series_equal()`

would raise an error when non-numeric dtypes were passed with`check_exact=True`

(GH 35446)Fixed regression in

`.groupby(..).rolling(..)`

where column selection was ignored (GH 35486)Fixed regression where

`DataFrame.interpolate()`

would raise a`TypeError`

when the`DataFrame`

was empty (GH 35598)Fixed regression in

`DataFrame.shift()`

with`axis=1`

and heterogeneous dtypes (GH 35488)Fixed regression in

`DataFrame.diff()`

with read-only data (GH 35559)Fixed regression in

`.groupby(..).rolling(..)`

where a segfault would occur with`center=True`

and an odd number of values (GH 35552)Fixed regression in

`DataFrame.apply()`

where functions that altered the input in-place only operated on a single row (GH 35462)Fixed regression in

`DataFrame.reset_index()`

would raise a`ValueError`

on empty`DataFrame`

with a`MultiIndex`

with a`datetime64`

dtype level (GH 35606, GH 35657)Fixed regression where

`pandas.merge_asof()`

would raise a`UnboundLocalError`

when`left_index`

,`right_index`

and`tolerance`

were set (GH 35558)Fixed regression in

`.groupby(..).rolling(..)`

where a custom`BaseIndexer`

would be ignored (GH 35557)Fixed regression in

`DataFrame.replace()`

and`Series.replace()`

where compiled regular expressions would be ignored during replacement (GH 35680)Fixed regression in

`aggregate()`

where a list of functions would produce the wrong results if at least one of the functions did not aggregate (GH 35490)Fixed memory usage issue when instantiating large

`pandas.arrays.StringArray`

(GH 35499)

## Bug fixes#

Bug in

`Styler`

whereby`cell_ids`

argument had no effect due to other recent changes (GH 35588) (GH 35663)Bug in

`pandas.testing.assert_series_equal()`

and`pandas.testing.assert_frame_equal()`

where extension dtypes were not ignored when`check_dtypes`

was set to`False`

(GH 35715)Bug in

`to_timedelta()`

fails when`arg`

is a`Series`

with`Int64`

dtype containing null values (GH 35574)Bug in

`.groupby(..).rolling(..)`

where passing`closed`

with column selection would raise a`ValueError`

(GH 35549)Bug in

`DataFrame`

constructor failing to raise`ValueError`

in some cases when`data`

and`index`

have mismatched lengths (GH 33437)

## Contributors#

A total of 20 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.

Ali McMaster

Daniel Saxton

Eric Goddard +

Fangchen Li

Isaac Virshup

Joris Van den Bossche

Kevin Sheppard

Matthew Roeschke

MeeseeksMachine +

Pandas Development Team

Richard Shadrach

Simon Hawkins

Terji Petersen

Tom Augspurger

Yutaro Ikeda +

attack68 +

edwardkong +

gabicca +

jbrockmendel

sanderland +