Quick example of parsing an obj format (https://groups.google.com/d/topic/python_inside_maya/ISwX-LOAcnc/discussion)

obj_parse.py

#!/usr/bin/env python
"""
Re: https://groups.google.com/d/topic/python_inside_maya/ISwX-LOAcnc/discussion
"""

class ObjProcessor(object):

    def __init__(self, filename):
        self.filename = filename 

        self._handlers = {
            "v": self._handleVert,
            "vn": self._handleNormal,
        }

    def process(self):
        """ Process the file """
        with open(self.filename) as f:

            if not self._validate(f):
                raise IOError("Bad file format: %s" % self.filename)

            handlers = self._handlers

            for line in f:
                # We don't want to handle blank lines or comments
                line = line.strip()
                if not line or line.startswith("#"):
                    continue

                tokens = line.strip().split()
                typ, args = tokens[0], tokens[1:]

                # Look up a registered handler for this type of line
                handler = handlers.get(typ)
                if not handler:
                    print "No registered handler for line (skipping):", line
                    continue

                # Delegate to our handler for the specific type
                handler(args)

    def _validate(self, fh):
        """
        Accept an open file handle, and determine if it is 
        an expected format. Returns True if validaton passes.
        Resets the file handle to the start when complete.
        """
        fh.seek(0)
        try:
            for line in fh:
                line = line.strip()
                # Loop until we get a non blank/comment line
                if not line or line.startswith('#'):
                    continue
                # Does our real line start with our expected char?
                return line.startswith('v')
        finally:
            fh.seek(0)

    def _handleVert(self, args):
        try:
            x, y, z = args
        except ValueError:
            print "handleVert: Ignoring bad args:", args
            return

        print "handleVert:", (float(x), float(y), float(z))

    def _handleNormal(self, args):
        try:
            x, y, z = args
        except ValueError:
            print "handleNormal: Ignoring bad args:", args
            return

        print "handleNormal:", (float(x), float(y), float(z))


if __name__ == "__main__":
    import sys
    obj = ObjProcessor(sys.argv[1])
    obj.process()