Java has string and string buffer concept.
Is there any concept of string buffer available in python?
Depends on what you want to do. If you want a mutable sequence, the builtin list type is your friend, and going from str to list and back is as simple as:
mystring = "abcdef" mylist = list(mystring) mystring = "".join(mylist)
If you want to build a large string using a for loop, the pythonic way is usually to build a list of strings then join them together with the proper separator (linebreak or whatever).
Else you can also use some text template system, or a parser or whatever specialized tool is the most appropriate for the job.