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I have a list of 18 data frames:

dfList = [df1, df2, df3, df4, df5, df6.....df18]

All of the data frames have a common id column so it's easy to join them each together with pd.merge 2 at a time. Is there a way to join them all at once so that dfList comes back as a single dataframe?

Fabio Lamanna
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Josh
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1 Answers1

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I think you need concat, but first set index of each DataFrame by common column:

dfs = [df.set_index('id') for df in dfList]
print pd.concat(dfs, axis=1)

If need join by merge:

from functools import reduce
df = reduce(lambda df1,df2: pd.merge(df1,df2,on='id'), dfList)
Jinhua Wang
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jezrael
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    `pd.concat(dfList, axis=1)` combined them all, but each df had it's own line (so every id was repeated 18 times) – Josh Aug 16 '16 at 15:00
  • I tried to write as variable: `sdf = pd.concat(dfs, axis=1)` and got `TypeError: first argument must be an iterable of pandas objects, you passed an object of type "DataFrame"` Don't get it. – Peter.k Feb 22 '19 at 16:59