Pandas insert alternate blank rows

Question

Given the following data frame:

import pandas as pd
import numpy as np
df1=pd.DataFrame({'A':['a','b','c','d'],
                 'B':['d',np.nan,'c','f']})
df1
    A   B
0   a   d
1   b   NaN
2   c   c
3   d   f

I'd like to insert blank rows before each row. The desired result is:

    A   B
0   NaN NaN
1   a   d
2   NaN NaN
3   b   NaN
4   NaN NaN
5   c   c
6   NaN NaN
7   d   f

In reality, I have many rows.

Thanks in advance!

Answer 1

I think you could change your index like @bananafish did and then use reindex:

df1.index = range(1, 2*len(df1)+1, 2)
df2 = df1.reindex(index=range(2*len(df1)))

In [29]: df2
Out[29]:
     A    B
0  NaN  NaN
1    a    d
2  NaN  NaN
3    b  NaN
4  NaN  NaN
5    c    c
6  NaN  NaN
7    d    f