How to get the common index of two pandas dataframes?

Question

I have two pandas DataFrames df1 and df2 and I want to transform them in order that they keep values only for the index that are common to the 2 dataframes.

df1

Answer 1

The index object has some set-like properties so you simply can take the intersection as follows:

df1 = df1.reindex[ df1.index & df2.index ]

This retains the order of the first dataframe in the intersection, df.