Simple Timer context manager. It will take care of starting the timer when your code block begins execution and stopping the timer when your code block ends.

timer.py

#! /usr/bin/env python
# -*- coding: utf-8 -*-
from time import clock


class Timer(object):
    def __init__(self, verbose=False):
        self.verbose = verbose

    def __enter__(self):
        self.start = clock()
        return self

    def __exit__(self, *args):
        self.end = clock()
        self.secs = self.end - self.start
        self.msecs = self.secs * 1000  # millisecs
        if self.verbose:
            print 'elapsed time: %f ms' % self.msecs

# Use case
if __name__ == "__main__":
    orignal_str = "Profiling a Python program is doing a dynamic analysis"\
        "that measures the execution time of the program and"\
        "everything that compose it."

    with Timer() as t:
        replace_str = ""
        for i, char in enumerate(orignal_str * 10000):
            c = char if char != " " else "-"
            replace_str += c
    print t.secs