[Python] Pandas - Interleave / Zip two DataFrames by row

Suppose I have two dataframes:

>> df1

0 1 2
0 a b c
1 d e f

>> df2

0 1 2
0 A B C
1 D E F


How can I interleave the rows? i.e. get this:

>> interleaved_df

0 1 2
0 a b c
1 A B C
2 d e f
3 D E F


(Note my real DFs have identical columns, but not the same number of rows).

What I've tried


inspired by this question (very similar, but asks on columns):

import pandas as pd
from itertools import chain, zip_longest

df1 = pd.DataFrame([['a','b','c'], ['d','e','f']])
df2 = pd.DataFrame([['A','B','C'], ['D','E','F']])

concat_df = pd.concat([df1,df2])

new_index = chain.from_iterable(zip_longest(df1.index, df2.index))
# new_index now holds the interleaved row indices

interleaved_df = concat_df.reindex(new_index)

ValueError: cannot reindex from a duplicate axis


The last call fails because df1 and df2 have some identical index values (which is also the case with my real DFs).

Any ideas?

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