How to duplicate Python dataframe one by one?

Question

I have a pandas.DataFrame as follows:

df1 = 
    a    b
0   1    2
1   3    4

I\'d like to make this three times to become:

Answer 1

You can use np.repeat

df = pd.DataFrame(np.repeat(df.values,[3,3], axis = 0), columns = df.columns)

You get

    a   b
0   1   2
1   1   2
2   1   2
3   3   4
4   3   4
5   3   4

Time testing:

%timeit pd.DataFrame(np.repeat(df.values,[3,3], axis = 0))
1000 loops, best of 3: 235 µs per loop

%timeit pd.concat([df] * 3).sort_index()
best of 3: 1.26 ms per loop

Numpy is definitely faster in most cases so no surprises there

EDIT: I am not sure if you would be looking for repeating indices but incase you do,

pd.DataFrame(np.repeat(df.values,3, axis = 0), index = np.repeat(df.index, 3), columns = df.columns)