Concat following row to the right of a df – python

I’m aiming to subset a pandas df using a condition and append those rows to the right of a df. For example, where Num2 is equal to 1, I want to take the following row and append it to the right of the df. The following appends every row, where as I just want to append the following row after a 1 in Num2. I’d also like to be able to append specific cols. Using below, this could be only Num1 and Num2.

df = pd.DataFrame({
            'Num1' : [0,1,2,3,4,4,0,1,2,3,1,1,2,3,4,0],
            'Num2' :  [0,0,0,0,0,1,3,0,1,2,0,0,0,0,1,4],
            'Value' :  [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
             })

df1 = df.add_suffix('1').join(df.shift(-1).add_suffix('2'))

intended output:

# grab all rows after a 1 in Num2
ones = df.loc[df["Num2"].shift().isin([1])]

# append these to the right
    Num1  Num2  Value  Num12  Num22
0      0     0      0
1      1     0      0
2      2     0      0
3      3     0      0
4      4     0      0
5      4     1      0      0      3      
6      0     3      0
7      1     0      0
8      2     1      0      3      2      
9      3     2      0
10     1     0      0
11     1     0      0
12     2     0      0
13     3     0      0
14     4     1      0      0      4      
15     0     4      0

Answer

You can try:

df=df.join(df.shift(-1).mask(df['Num2'].ne(1)).drop('Value',1).add_suffix('2')) 

OR

ones.index=ones.index-1
df=df.join(ones.drop('Value',1).add_suffix('2'))
#OR(use any 1 since both method doing the same thing)
df=pd.concat([df,ones.drop('Value',1).add_suffix('2')],axis=1)

If needed use fillna():

df[["Num12", "Num22"]]=df[["Num12", "Num22"]].fillna('')