Accessor behavior variances with multiindex

[allComputableThings]

Code Sample, a copy-pastable example if possible

def gen():
    yield '1','2',1,2
    yield '1','2',1,2
    yield '1','3',3,2
    yield '2','4',1,2

ser = pd.DataFrame(gen(), columns=["a", "b", "c", "d",]).set_index(["a", "b"])["c"]
print ser

print ser.loc[('1','3')]
print ser.at[('1','3')]  # TypeError: _get_value() got multiple values for keyword argument 'takeable'

Problem description

The .at accessor should return the indexed value 3.

There doesn't seem any way reliably look up a single scalar in a multiindex. If this is not supported, a better error would be appreciated.

Expected Output

3

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 2.7.6.final.0
python-bits: 64
OS: Linux
OS-release: 3.13.0-24-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.22.0
pytest: None
pip: 9.0.1
setuptools: 36.0.1
Cython: 0.27.3
numpy: 1.14.0
scipy: 1.0.0
pyarrow: None
xarray: None
IPython: 5.3.0
sphinx: None
patsy: 0.2.1
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: 3.1.1
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 1.7.0
xlrd: 0.9.2
xlwt: 0.7.5
xlsxwriter: None
lxml: None
bs4: None
html5lib: 0.999999999
sqlalchemy: 1.0.15
pymysql: None
psycopg2: 2.7.3.2 (dt dec pq3 ext lo64)
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

[allComputableThings]

Seems related to: #9259

[allComputableThings]

An expanded example with even more weirdness.

It seems that, if I want to assign a new row, or lookup an existing row in a series or dataframe, I need to choose different accessors depending on whether the multindex label is defined for all indexes.

def gen():
    yield 's',None,'sval'

ser = pd.DataFrame(gen(), columns=["a", "b", "c", ]).set_index(["a", "b"])["c"]
print ser

# Writing ---

#ser[('s1',)] = "z" # AttributeError: 'float' object has no attribute 'axes'
ser.at[('s2',)] = "z" # success
#ser.loc[('s3',)] = "z" # AttributeError: 'float' object has no attribute 'axes'

ser[('s4','x')] = "z" # success
#ser.at[('s5','x')] = "z" # ValueError: Not enough indexers for scalar access (setting)!
ser.loc[('s6','x')] = "z" # success

# Reading ---

print type(ser.loc[('s6','x')])  # Success => scalar
#print type(ser.at[('s6','x')])  # _get_value() got multiple values for keyword argument 'takeable'
print type(ser[('s6','x')])    # Success => scalar

print type(ser.loc[('s2',)])  # Success => series
#print type(ser.at[('s2',)])  # AttributeError: 'numpy.ndarray' object has no attribute '_values'
print type(ser[('s2',)])      # Success => series

[jreback]

this is a duplicate of #9259

.iat/.at are not too multi-index aware currently.

[allComputableThings]

I guess if you leave it open, someone could work on it. Unless, there’s a good reason to want this feature

…

On Mon, Feb 26, 2018 at 5:04 PM Jeff Reback ***@***.***> wrote: this is a duplicate of #9259 <#9259> .iat/.at are not too multi-index aware currently. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#19916 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHcErMKNd8wHAv0PlK415kc3XaZIoanvks5tY1S2gaJpZM4ST06R> .