#! /usr/bin/env python """Tool for measuring execution time of small code snippets. This module avoids a number of common traps for measuring executiontimes.  See also Tim Peters' introduction to the Algorithms chapter inthe Python Cookbook, published by O'Reilly. Library usage: see the Timer class. Command line usage:    python timeit.py [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement] Options:  -n/--number N: how many times to execute 'statement' (default: see below)  -r/--repeat N: how many times to repeat the timer (default 3)  -s/--setup S: statement to be executed once initially (default 'pass')  -t/--time: use time.time() (default on Unix)  -c/--clock: use time.clock() (default on Windows)  -v/--verbose: print raw timing results; repeat for more digits precision  -h/--help: print this usage message and exit  statement: statement to be timed (default 'pass') A multi-line statement may be given by specifying each line as aseparate argument; indented lines are possible by enclosing anargument in quotes and using leading spaces.  Multiple -s options aretreated similarly. If -n is not given, a suitable number of loops is calculated by tryingsuccessive powers of 10 until the total time is at least 0.2 seconds. The difference in default timer function is because on Windows,clock() has microsecond granularity but time()'s granularity is 1/60thof a second; on Unix, clock() has 1/100th of a second granularity andtime() is much more precise.  On either platform, the default timerfunctions measure wall clock time, not the CPU time.  This means thatother processes running on the same computer may interfere with thetiming.  The best thing to do when accurate timing is necessary is torepeat the timing a few times and use the best time.  The -r option isgood for this; the default of 3 repetitions is probably enough in mostcases.  On Unix, you can use clock() to measure CPU time. Note: there is a certain baseline overhead associated with executing apass statement.  The code here doesn't try to hide it, but you shouldbe aware of it.  The baseline overhead can be measured by invoking theprogram without arguments. The baseline overhead differs between Python versions!  Also, tofairly compare older Python versions to Python 2.3, you may want touse python -O for the older versions to avoid timing SET_LINENOinstructions.""" import gcimport sysimport timetry:    import itertoolsexcept ImportError:    # Must be an older Python version (see timeit() below)    itertools = None __all__ = ["Timer"] dummy_src_name = "<timeit-src>"default_number = 1000000default_repeat = 3 if sys.platform == "win32":    # On Windows, the best timer is time.clock()    default_timer = time.clockelse:    # On most other platforms the best timer is time.time()    default_timer = time.time # Don't change the indentation of the template; the reindent() calls# in Timer.__init__() depend on setup being indented 4 spaces and stmt# being indented 8 spaces.template = """def inner(_it, _timer):    %(setup)s    _t0 = _timer()    for _i in _it:        %(stmt)s    _t1 = _timer()    return _t1 - _t0""" def reindent(src, indent):    """Helper to reindent a multi-line statement."""    return src.replace("\n", "\n" + " "*indent) class Timer:    """Class for timing execution speed of small code snippets.     The constructor takes a statement to be timed, an additional    statement used for setup, and a timer function.  Both statements    default to 'pass'; the timer function is platform-dependent (see    module doc string).     To measure the execution time of the first statement, use the    timeit() method.  The repeat() method is a convenience to call    timeit() multiple times and return a list of results.     The statements may contain newlines, as long as they don't contain    multi-line string literals.    """     def __init__(self, stmt="pass", setup="pass", timer=default_timer):        """Constructor.  See class doc string."""        self.timer = timer        stmt = reindent(stmt, 8)        setup = reindent(setup, 4)        src = template % {'stmt': stmt, 'setup': setup}        self.src = src # Save for traceback display        code = compile(src, dummy_src_name, "exec")        ns = {}        exec code in globals(), ns        self.inner = ns["inner"]     def print_exc(self, file=None):        """Helper to print a traceback from the timed code.         Typical use:             t = Timer(...)       # outside the try/except            try:                t.timeit(...)    # or t.repeat(...)            except:                t.print_exc()         The advantage over the standard traceback is that source lines        in the compiled template will be displayed.         The optional file argument directs where the traceback is        sent; it defaults to sys.stderr.        """        import linecache, traceback        linecache.cache[dummy_src_name] = (len(self.src),                                           None,                                           self.src.split("\n"),                                           dummy_src_name)        traceback.print_exc(file=file)     def timeit(self, number=default_number):        """Time 'number' executions of the main statement.         To be precise, this executes the setup statement once, and        then returns the time it takes to execute the main statement        a number of times, as a float measured in seconds.  The        argument is the number of times through the loop, defaulting        to one million.  The main statement, the setup statement and        the timer function to be used are passed to the constructor.        """        if itertools:            it = itertools.repeat(None, number)        else:            it = [None] * number        gcold = gc.isenabled()        gc.disable()        timing = self.inner(it, self.timer)        if gcold:            gc.enable()        return timing     def repeat(self, repeat=default_repeat, number=default_number):        """Call timeit() a few times.         This is a convenience function that calls the timeit()        repeatedly, returning a list of results.  The first argument        specifies how many times to call timeit(), defaulting to 3;        the second argument specifies the timer argument, defaulting        to one million.         Note: it's tempting to calculate mean and standard deviation        from the result vector and report these.  However, this is not        very useful.  In a typical case, the lowest value gives a        lower bound for how fast your machine can run the given code        snippet; higher values in the result vector are typically not        caused by variability in Python's speed, but by other        processes interfering with your timing accuracy.  So the min()        of the result is probably the only number you should be        interested in.  After that, you should look at the entire        vector and apply common sense rather than statistics.        """        r = []        for i in range(repeat):            t = self.timeit(number)            r.append(t)        return r def main(args=None):    """Main program, used when run as a script.     The optional argument specifies the command line to be parsed,    defaulting to sys.argv[1:].     The return value is an exit code to be passed to sys.exit(); it    may be None to indicate success.     When an exception happens during timing, a traceback is printed to    stderr and the return value is 1.  Exceptions at other times    (including the template compilation) are not caught.    """    if args is None:        args = sys.argv[1:]    import getopt    try:        opts, args = getopt.getopt(args, "n:s:r:tcvh",                                   ["number=", "setup=", "repeat=",                                    "time", "clock", "verbose", "help"])    except getopt.error, err:        print err        print "use -h/--help for command line help"        return 2    timer = default_timer    stmt = "\n".join(args) or "pass"    number = 0 # auto-determine    setup = []    repeat = default_repeat    verbose = 0    precision = 3    for o, a in opts:        if o in ("-n", "--number"):            number = int(a)        if o in ("-s", "--setup"):            setup.append(a)        if o in ("-r", "--repeat"):            repeat = int(a)            if repeat <= 0:                repeat = 1        if o in ("-t", "--time"):            timer = time.time        if o in ("-c", "--clock"):            timer = time.clock        if o in ("-v", "--verbose"):            if verbose:                precision += 1            verbose += 1        if o in ("-h", "--help"):            print __doc__,            return 0    setup = "\n".join(setup) or "pass"    # Include the current directory, so that local imports work (sys.path    # contains the directory of this script, rather than the current    # directory)    import os    sys.path.insert(0, os.curdir)    t = Timer(stmt, setup, timer)    if number == 0:        # determine number so that 0.2 <= total time < 2.0        for i in range(1, 10):            number = 10**i            try:                x = t.timeit(number)            except:                t.print_exc()                return 1            if verbose:                print "%d loops -> %.*g secs" % (number, precision, x)            if x >= 0.2:                break    try:        r = t.repeat(repeat, number)    except:        t.print_exc()        return 1    best = min(r)    if verbose:        print "raw times:", " ".join(["%.*g" % (precision, x) for x in r])    print "%d loops," % number,    usec = best * 1e6 / number    if usec < 1000:        print "best of %d: %.*g usec per loop" % (repeat, precision, usec)    else:        msec = usec / 1000        if msec < 1000:            print "best of %d: %.*g msec per loop" % (repeat, precision, msec)        else:            sec = msec / 1000            print "best of %d: %.*g sec per loop" % (repeat, precision, sec)    return None if __name__ == "__main__":    sys.exit(main())