Tool Module Description cat tac Concatenate.py Concatenate.py CutPaste.py Concatenate files and print on the standard output Concatenate and print files in reverse Remove sections from each line of files cut paste CutPaste.py Merge lines of files grep head tail Grep.py Partial.py Partial.py Sorting.py WordCount.py Print lines of files matching a pattern Output the first part of files Output the last part of files Sort lines of text files Print newline, word, and byte counts for each file sort WC paste Paste joins two or more files together, inserting a comma in between $ python src/tt.py paste data/let3 dataum2 a,1 b,2 Paste works by opening each file listed on the command line and storing the resulting file object in a list. Then a for loop iterates over the list of file objects, reading one line from each file and printing it with a comma instead of a newline. After the last file is read a newline is printed. The for loop over the files is repeated until all files are exhausted. The output of the paste command is as long as the longest file; missing fields are just empty strings