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 numpy.repeat with parameter scalar 3 and then add columns parameter to DataFrame constructor:

df = pd.DataFrame(np.repeat(df.values, 3, axis=0), columns=df.columns)
print (df)
   a  b
0  1  2
1  1  2
2  1  2
3  3  4
4  3  4
5  3  4

If really want duplicated index what can complicated some pandas functions like reindex which failed:

r = np.repeat(np.arange(len(df.index)), 3)
df = pd.DataFrame(df.values[r], df.index[r], df.columns)
print (df)
   a  b
0  1  2
0  1  2
0  1  2
1  3  4
1  3  4
1  3  4