simple python context manager

ctx.py

# -*- coding: utf-8 -*-


class Greetings(object):

  def __init__(self):
    self.text = 'hello world'

  def say(self):
    print 'My engine is: %s' % self.text


class switch_text(object):

  def __init__(self, instance, new_text):
    self.instance = instance
    self.original_text = self.instance.text
    self.new_text = new_text

  def __enter__(self):
    self.instance.text = self.new_text
    return self.instance

  def __exit__(self, t, value, traceback):
    self.instance.text = self.original_text


if __name__ == '__main__':
  greetings = Greetings()
  greetings.say()
  with switch_text(greetings, 'Hello there') as greeting:
    greeting.say()
  greetings.say()