Python execution timing context manager class

timer.py

import time
class Timer(object):

	def __init__(self, echo=False):
		self._start = 0.0
		self._stop = 0.0
		self.echo = echo

	def __enter__(self):
		self._start = time.time()
		return self

	def __exit__(self, type, value, traceback):
		self._stop = time.time()
		if self.echo:
			if isinstance(self.echo, basestring):
				print self.echo, self
			else:
				print self

	def __float__(self):
		return float(self._stop - self._start)

	def __str__(self):
		return str(float(self))
	__repr__ = __str__