Join result takes the index order of the other (right) DataFrame instead of the calling's (left) one · Issue #15582 · pandas-dev/pandas (original) (raw)

Code Sample, a copy-pastable example if possible

Your code here

df1 = pd.DataFrame({'a': [0, 10, 20]}) df2 = pd.DataFrame({'b': [200, 100]}, index=[2,1])

print(df1.join(df2, how='inner')) print(df2.join(df1, how='inner'))

print(df1.join(df2, how='inner', sort=True))

Problem description

Contrary to what is stated in the documentation of DataFrame.join(), when using the default sort=False, the return DataFrame preserves the index order of the other (right) DataFrame, instead of the index order of the calling (left) DataFrame.

Besides, the sort=True argument does not work.

Expected Output

The expected output is that the return DataFrame should preserve the index order of the calling (left) DataFrame.

Output of pd.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.5.2.final.0 python-bits: 64 OS: Linux OS-release: 3.13.0-108-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: ca_ES.UTF-8 LOCALE: ca_ES.UTF-8

pandas: 0.19.2
nose: 1.3.7
pip: 8.1.2
setuptools: 27.2.0.post20161106
Cython: 0.24.1
numpy: 1.11.1
scipy: 0.18.1
statsmodels: 0.6.1
xarray: None
IPython: 5.1.0
sphinx: 1.4.6
patsy: 0.4.1
dateutil: 2.5.3
pytz: 2016.6.1
blosc: None
bottleneck: 1.1.0
tables: 3.2.3.1
numexpr: 2.6.1
matplotlib: 1.5.3
openpyxl: 2.3.2
xlrd: 1.0.0
xlwt: 1.1.2
xlsxwriter: 0.9.3
lxml: 3.6.4
bs4: 4.5.1
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.0.13
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.42.0
pandas_datareader: 0.2.1