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BUG: keys argument in pandas.concat does not preserve Index name #14252

wesm opened this Issue Sep 19, 2016 · 0 comments


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2 participants

wesm commented Sep 19, 2016

Code Sample, a copy-pastable example if possible

df = pd.DataFrame({'foo': [1, 2, 3, 4],
                   'bar': [0.1, 0.2, 0.3, 0.4]})
index = pd.Index(['a', 'b'], name='baz')

concatted = pd.concat([df, df], keys=index)

## -- End pasted text --
Out[3]: FrozenList([None, None])

Expected Output

FrozenList(['baz', None])

output of pd.show_versions()

A few days older than master:

commit: 5e2f9da6e8e713bd89cfe8760e63583ea7d29879

@jreback jreback added this to the Next Major Release milestone Sep 19, 2016

@jreback jreback added the Reshaping label Sep 19, 2016

@rsmith54 rsmith54 referenced this issue Sep 20, 2016


BUG: fix for GH14252 #14261

4 of 4 tasks complete

@bkandel bkandel referenced this issue Sep 23, 2016


BUG: Fix concat key name #14292

4 of 4 tasks complete

@jreback jreback modified the milestones: 0.19.1, Next Major Release Oct 8, 2016

@jreback jreback closed this in 16b64f1 Oct 9, 2016

tworec pushed a commit to RTBHOUSE/pandas that referenced this issue Oct 21, 2016

Ben Kandel Piotr Chromiec
BUG: Fix concat key name
closes #14252
Fixes a bug where `pd.concat` didn't propagate the names of keys used to
create  a hierarchical index.

Author: Ben Kandel <>

Closes #14292 from bkandel/fix_concat_key_name and squashes the following commits:

cdc76f6 [Ben Kandel] take out _ensure_index
4a301f8 [Ben Kandel] put back in Index coercion
d8e2c17 [Ben Kandel] remove coercion to Index before _ensure_index
44932cc [Ben Kandel] changed whatsnew entry to 0.19.1
c51df19 [Ben Kandel] _ensure_index
b54b081 [Ben Kandel] simplified logic
3256119 [Ben Kandel] typo
789ecd4 [Ben Kandel] use _ensure_index
350e724 [Ben Kandel] simplified logic
9615a69 [Ben Kandel] extra tests
5c0108b [Ben Kandel] comments
dd3c4cc [Ben Kandel] comments
5cd8392 [Ben Kandel] added test for names
bc5f1fb [Ben Kandel] cleanup
ef6db68 [Ben Kandel] BUG: Propagate key names in concat.
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