adding rows with Nan values to Pandas DataFrame

Question

I want to insert rows with Nan values after each row

index	values
0	44
1	50
2	51
3	66
4	23

DataFrame should look like this

index	values
0	44
1	Nan
2	50
3	Nan
4	51
5	Nan
6	66
7	Nan
8	23

Answer 1

Use concat with DataFrame filled by NaNs and same indices and then use DataFrame.sort_index:

df = (pd.concat([df, pd.DataFrame(index=df.index)])
        .sort_index(kind='stable', ignore_index=True))
print (df)
   values
0    44.0
1     NaN
2    50.0
3     NaN
4    51.0
5     NaN
6    66.0
7     NaN
8    23.0
9     NaN

If need remove last missing value:

df = (pd.concat([df, pd.DataFrame(index=df.index)])
        .sort_index(kind='stable', ignore_index=True)
        .iloc[:-1])
print (df)
   values
0    44.0
1     NaN
2    50.0
3     NaN
4    51.0
5     NaN
6    66.0
7     NaN
8    23.0