Pandas return DataFrame from apply function?

Question

sdf = sdf['Name1'].apply(lambda x: tryLookup(x, tdf))

tryLookup is a function that is currently taking a string, which is the value of Name1 in the sdf column. We map the function using apply to every row in the sdf DataFrame.

Instead of tryLookup returning just a string, is there a way for tryLookup to return a DataFrame that I want to merge with the sdf DataFrame? tryLookup has some extra information, and I want to include that in the results by adding them as new columns to all the rows in sdf.

So the return for tryLookup is as such:

return pd.Series({'BEST MATCH': bestMatch, 'SIMILARITY SCORE': humanScore})

I tried something such as

sdf = sdf.merge(sdf['Name1'].apply(lambda x: tryLookup(x, tdf)), left_index=True, right_index=True)

But that just throws

Traceback (most recent call last):
  File "lookup.py", line 160, in <module>
    main()
  File "lookup.py", line 40, in main
    sdf = sdf.merge(sdf['Name1'].apply(lambda x: tryLookup(x, tdf)), left_index=True, right_index=True)
  File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 4618, in merge
    copy=copy, indicator=indicator)
  File "C:\Python27\lib\site-packages\pandas\tools\merge.py", line 58, in merge
    copy=copy, indicator=indicator)
  File "C:\Python27\lib\site-packages\pandas\tools\merge.py", line 473, in __init__
    'type {0}'.format(type(right)))
ValueError: can not merge DataFrame with instance of type <class 'pandas.core.series.Series'>

Any help would be great. Thanks.

Are you looking for pd.lookup?pandas.pydata.org/pandas-docs/stable/generated/… — BENY
– BENY, Commented Sep 14, 2017 at 16:46

Mohamed Ali JAMAOUI · Accepted Answer · 2017-09-14 17:43:32Z

1

Try converting the pd.Series to a dataframe with pandas.Series.to_frame as documented here:

sdf = sdf.merge(sdf['Sold To Name (10)'].apply(lambda x: tryLookup(x, tdf)).to_frame(), left_index=True, right_index=True)

edited Sep 14, 2017 at 17:43

answered Sep 14, 2017 at 16:47

Mohamed Ali JAMAOUI

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1 Comment

X33 Over a year ago

sdf is a DataFrame in this case.

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