text: #! /usr/bin/python2.4
  
  """Tool for measuring execution time of small code snippets.
  
  This module avoids a number of common traps for measuring execution
  times.  See also Tim Peters' introduction to the Algorithms chapter in
  the 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 a
  separate argument; indented lines are possible by enclosing an
  argument in quotes and using leading spaces.  Multiple -s options are
  treated similarly.
  
  If -n is not given, a suitable number of loops is calculated by trying
  successive 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 1/60th
  of a second; on Unix, clock() has 1/100th of a second granularity and
  time() is much more precise.  On either platform, the default timer
  functions measure wall clock time, not the CPU time.  This means that
  other processes running on the same computer may interfere with the
  timing.  The best thing to do when accurate timing is necessary is to
  repeat the timing a few times and use the best time.  The -r option is
  good for this; the default of 3 repetitions is probably enough in most
  cases.  On Unix, you can use clock() to measure CPU time.
  
  Note: there is a certain baseline overhead associated with executing a
  pass statement.  The code here doesn't try to hide it, but you should
  be aware of it.  The baseline overhead can be measured by invoking the
  program without arguments.
  
  The baseline overhead differs between Python versions!  Also, to
  fairly compare older Python versions to Python 2.3, you may want to
  use python -O for the older versions to avoid timing SET_LINENO
  instructions.
  """
  
  import gc
  import sys
  import time
  try:
      import itertools
  except ImportError:
      # Must be an older Python version (see timeit() below)
      itertools = None
  
  __all__ = ["Timer"]
  
  dummy_src_name = "<timeit-src>"
  default_number = 1000000
  default_repeat = 3
  
  if sys.platform == "win32":
      # On Windows, the best timer is time.clock()
      default_timer = time.clock
  else:
      # 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())
  