UNIX for Beginners Questions & Answers

from itertools import izip

   with open("textfile1") as textfile1, open("textfile2") as textfile2: 
   for x, y in izip(textfile1, textfile2):
    x = x.strip()
    y = y.strip()
    print("{0}{0}".format(x, y))

paste -d ' ' a b   

1  a                        
2  b                       
3  c                       
4  d                       
5  e                      
6                               
7                               
8                                 
9

1  ↓                          
2  a                       
3  b                       
4  c                       
5  d                       
6  e                       
7                               
8                               
9                               

1                               
2                               
3  ↓                          
4  a                      
5  b                       
6  c                       
7  d                       
8  e                       
9

                 
1  b                       
2  c                       
3  d                       
4  e                             
5                               
6                               
7  ↓                          
8  List is about to loop        
9  a