Simple static file handler for Falcon

static.py

import falcon
import mimetypes
import os.path
from falcon.request import Request
from falcon.response import Response


# simple static file handler for falcon
# it is recommended to use a program like nginx to handle static files
# however this is useful for development and when performance is not a priority
class StaticHandler:
    def __init__(self, directory_index: [str] = None):
        self.directory_index = directory_index or ['index.html', 'index.htm']
        self.prefix = None  # type: str
        self.static_path = None  # type: str

    def on_get(self, req: Request, res: Response) -> None:
        # should always start with prefix
        # if not req.path.startswith(self.prefix): return

        # remove prefix from path and remove leading / if possible
        file = req.path[len(self.prefix):]
        if len(file) > 0 and file.startswith('/'): file = file[1:]

        # join static path and file path
        file = os.path.join(self.static_path, file)
        file = os.path.abspath(file)

        # do not allow to use paths on the top level of self.static_path
        # this prevents using urls such as http://127.0.0.1:8080/../package.json
        if not file.startswith(self.static_path):
            res.status = falcon.HTTP_403
            return

        # if file is a directory try to guess index name
        if os.path.isdir(file):

            initial_file = file

            for index_file in self.directory_index:
                tmp = os.path.join(file, index_file)
                if os.path.isfile(tmp):
                    file = tmp
                    break

            # if file has not changed return 404
            if initial_file == file:
                res.status = falcon.HTTP_404
                return

        # get type and encoding from current filename
        t, e = mimetypes.guess_type(file)
        if t is not None: res.content_type = t

        # try to return file
        try:
            with open(file, 'rb') as f:
                res.body = f.read()

        # if error happened print error and return 404
        except FileNotFoundError as e:
            print(e)
            res.status = falcon.HTTP_404

    def enable(self, api: falcon.API, prefix: str, static_path: str) -> None:
        self.prefix = prefix
        self.static_path = static_path
        api.add_sink(self.on_get, self.prefix)

This worked as long as I commented out lines 31-33.