Class which will always give the fresh contents of a file

freshfile.py

import codecs
from os.path import getmtime
from time import time


class FreshFile(object):

    def __init__(self, filename, mode='r', encoding='utf-8', process_func=None,
                 max_age=0):
        self._filename = filename
        self._mode = mode
        self._encoding = encoding

        self._process_func = process_func
        self._max_age = max_age
        self._last_read = 0

        self._result_mtime = 0
        self._result = None

    @property
    def fresh_val(self):
        with codecs.open(self._filename, self._mode, self._encoding) as f:
            self._result = f.read()

        if self._process_func:
            self._result = self._process_func(self._result)

        self._result_mtime = getmtime(self._filename)
        return self._result

    @property
    def val(self):
        if self._max_age:
            now = time()
            if self._result and now - self._last_read < self._max_age:
                return self._result
            self._last_read = now

        if self._result and self._result_mtime == getmtime(self._filename):
            return self._result

        return self.fresh_val