append spliter row after rows which contains 'REL' in action column

I would like to add a split row after row which continas "REL" keyword.

import pandas as pd
data = [
    [1,'ACQ','A'],
    [2,'REL','A'],
    [3,'ACQ','B'],
    [4,'REL','B'],
    [5,'ACQ','C'],
    [6,'REL','C'],
    [7,'ACQ','A'],
    [8,'REL','A']
    ]
df = pd.DataFrame(data,columns=['x','action','name'])
print(df)

Expected output:

   x action name
0  1    ACQ    A
1  2    REL    A
2  3    ACQ    B
3  4    REL    B
4  5    ACQ    C
5  6    REL    C
6  7    ACQ    A
7  8    REL    A
      x action name
0   1.0    ACQ    A
1   2.0    REL    A
2   NaN    NaN  NaN
3   3.0    ACQ    B
4   4.0    REL    B
5   NaN    NaN  NaN
6   5.0    ACQ    C
7   6.0    REL    C
8   NaN    NaN  NaN
9   7.0    ACQ    A
10  8.0    REL    A
11  NaN    NaN  NaN

>Solution :

You could try with reindex

out = df.reindex(df.index.union(df.index[df.action=='REL']+0.5))
Out[22]: 
       x action name
0.0  1.0    ACQ    A
1.0  2.0    REL    A
1.5  NaN    NaN  NaN
2.0  3.0    ACQ    B
3.0  4.0    REL    B
3.5  NaN    NaN  NaN
4.0  5.0    ACQ    C
5.0  6.0    REL    C
5.5  NaN    NaN  NaN
6.0  7.0    ACQ    A
7.0  8.0    REL    A
7.5  NaN    NaN  NaN