Example of a class which can be used as a decorator or context manager.

throttle.py

import time
from functools import wraps

class throttle(object):

    """Throttle calls to a method by `factor'."""

    def __init__(self, factor, error_only=False):
        self.factor = factor
        self.error_only = error_only
        self.start_time = None

    def __enter__(self):
        """Enter the nested context."""
        self.start_time = time.time()

    def __exit__(self, type, value, traceback):
        """Exit the nested context."""
        if not self.error_only or (self.error_only and type):
            time.sleep(self.factor * (time.time() - self.start_time))
        return False

    def __call__(self, function):
        """Act as a decorator."""
        @wraps(function)
        def __inner__(*args, **kwargs):
            with self:
                return function(*args, **kwargs)

        return __inner__

@throttle(2)
def test_one():
    print "I will be throttled for 2s."
    time.sleep(1)


def test_two():
    with throttle(2):
        print "I will be throttled for 2s."
        time.sleep(1)


if __name__ == '__main__':
    s = time.time()
    test_one()
    print time.time() - s

    print

    s = time.time()
    test_two()
    print time.time() - s