Code Sample
import numpy as np
import pandas as pd
index = np.linspace(-3, 5, 7)
df = pd.DataFrame({'A': np.sin(index), 'B': np.cos(index**2)}, index=index)
type(df.apply(np.sum, axis=1, reduce=False))
Problem description
The docs say "If reduce is True a Series will always be returned, and if False a DataFrame will always be returned".
The type returned is a pandas.core.series.Series even though I set reduce=False
Expected Output
Output of pd.show_versions()
INSTALLED VERSIONS
------------------
commit: None
python: 3.6.2.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None
pandas: 0.20.3
pytest: 3.2.1
pip: 9.0.1
setuptools: 36.5.0.post20170921
Cython: 0.26.1
numpy: 1.13.1
scipy: 0.19.1
xarray: None
IPython: 6.1.0
sphinx: 1.6.3
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 2.4.8
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 0.9.8
lxml: 3.8.0
bs4: 4.6.0
html5lib: 0.999999999
sqlalchemy: 1.1.13
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None
Comment From: apopescu
Actually the docs are saying If the DataFrame is empty, apply will use reduce to determine whether the result should be a Series or a DataFrame. So i think what are you saying is true, but only for empties Dataframes.
Code sample:
df = pd.DataFrame()
type(df.apply(np.sum, axis=1, reduce=False))
pandas.core.frame.DataFrame
type(df.apply(np.sum, axis=1, reduce=True))
pandas.core.series.Series
Comment From: jreback
yeah the reduce arg is a bit of a red-herring. will be changing this after #18577, and incorporating this to result_type I think.
However this usage is functioning according to the docs.
thanks @apopescu
