gistfile1.txt

#!/usr/bin/env python

import cgi

class safe:
	def __init__(this, text):
		this.content = text
	def __str__(this):
		return safe.current_method(this)
	def as_is(this):
		return this.content
	def as_html(this):
		return cgi.escape(this.content, 1)
	@staticmethod
	def use(new_way):
		if (new_way == "old"):
			safe.current_method = safe.stack.pop()
		else:
			safe.stack.append( safe.current_method )
			safe.current_method = safe.table[ new_way ]
safe.stack = []
safe.current_method = safe.as_is
safe.table = { "html" : safe.as_html, "text" : safe.as_is }

x = safe("<b>foo</b>")
print "x1=", x

safe.use("html")
print "x2=", x

safe.use("old")
print "x3=", x