So here is what I envision: I write the main application in Python. I write a (hopefully) small Haskell module that: a) Calls back to the main Python app for reading the text to be parsed, preferably using laziness. b) Parses the text, and maybe processes a bit. c) Returns the parsed data-structure. (This may be tricky, but I think I know how to do it).
You might be able to get away with running the Haskell program as a separate process, communicating via pipes. Look at Posix.popen (not available in the new libraries yet):
http://www.haskell.org/ghc/docs/latest/html/hslibs/popen.html
This is probably easier to achieve than trying to link the programs together, but it does limit you to bytestream communication both ways.
--KW 8-)
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Keith Wansbrough