Concatenating two fields which have multiple values separated by delimiter using pandas

I have source csv file with structure as:

Col1, Col2, Col3, Col4
123, John, ID1|ID2|ID3, Lisbon|Kite|Dam
456, Tree, ID4|ID9|ID10|ID11, Chart||Cam|Dare
543, Jam, ID12, Jar

I need to concatenate the col3 and col4 values by maintaining the sequence and order of pipe(delimiter). The CombinedCol should also be a pipe separated column like below:

Col1, Col2, CombinedCol
123, John, ID1:Lisbon|ID2:Kite|ID3:Dam
456, Tree, ID4:Chart|ID9|ID10:Cam|ID11:Dare
543, Jam, ID12:Jar

I am trying this using pandas but I am stuck and not able to iterate the field values at the column

df['CombinedCol']=df['Col3'].str.split('|')+':'+df['Col4'].str.split('|')

>Solution :

Use list comparehension with double zip – by splitted values by |, then zip and join by : and last join by | to new column:

zipped = zip(df['Col3'], df['Col4'])

df['CombinedCol'] = ['|'.join(':'.join(y).rstrip(':') 
                      for y in zip(a.split('|'), b.split('|'))) 
                      for a, b in zipped]
print (df)
   Col1  Col2               Col3             Col4  \
0   123  John        ID1|ID2|ID3  Lisbon|Kite|Dam   
1   456  Tree  ID4|ID9|ID10|ID11  Chart||Cam|Dare   
2   543   Jam               ID12              Jar   

                        CombinedCol  
0       ID1:Lisbon|ID2:Kite|ID3:Dam  
1  ID4:Chart|ID9|ID10:Cam|ID11:Dare  
2                          ID12:Jar