TypeError for mixed-type indices in python3

Code Sample, a copy-pastable example if possible

import pandas as pd
import numpy as np
table = pd.DataFrame(data=np.random.randn(5,2), index=[4,1,'foo',3,'bar'])
table = table.sort_index()

Problem description

The code above works in python2. However, in python3 a TypeError is raised:

TypeError: '<' not supported between instances of 'str' and 'int'

The reason for this is described here: mixed-type sequencing cannot be sorted anymore just like this.

Expected Output

No exception when calling sort_index in python3.

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None

pandas: 0.22.0 pytest: None pip: 10.0.0 setuptools: 39.0.1 Cython: None numpy: 1.14.2 scipy: 1.0.1 pyarrow: None xarray: None IPython: 6.3.1 sphinx: None patsy: None dateutil: 2.7.2 pytz: 2018.4 blosc: None bottleneck: None tables: None numexpr: None feather: None matplotlib: 2.2.2 openpyxl: None xlrd: None xlwt: None xlsxwriter: None lxml: None bs4: None html5lib: None sqlalchemy: None pymysql: None psycopg2: None jinja2: None s3fs: None fastparquet: None pandas_gbq: None pandas_datareader: None

[mroeschke]

This looks like a duplicate of https://github.com/pandas-dev/pandas/issues/17010. Closing

[jreback]

this is using pandas in a very non-idiomatic way as mixed types are not easily represented, except by object type. that said, the sorting mechanisms internally for object types could use safe_sort (see pandas.core.sorting) which handles correctly these mixed types cases