text: #! /usr/bin/env python3
  
  """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] [-p] [-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').
                  Execution time of this setup statement is NOT timed.
    -p/--process: use time.process_time() (default is time.perf_counter())
    -t/--time: use time.time() (deprecated)
    -c/--clock: use time.clock() (deprecated)
    -v/--verbose: print raw timing results; repeat for more digits precision
    -u/--unit: set the output time unit (usec, msec, or sec)
    -h/--help: print this usage message and exit
    --: separate options from statement, use when statement starts with -
    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.
  
  Note: there is a certain baseline overhead associated with executing a
  pass statement.  It differs between versions.  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.
  
  Classes:
  
      Timer
  
  Functions:
  
      timeit(string, string) -> float
      repeat(string, string) -> list
      default_timer() -> float
  
  """
  
  import gc
  import sys
  import time
  import itertools
  
  __all__ = ["Timer", "timeit", "repeat", "default_timer"]
  
  dummy_src_name = "<timeit-src>"
  default_number = 1000000
  default_repeat = 3
  default_timer = time.perf_counter
  
  _globals = globals
  
  # 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{init}):
      {setup}
      _t0 = _timer()
      for _i in _it:
          {stmt}
      _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).  If 'globals' is specified, the code will be
      executed within that namespace (as opposed to inside timeit's
      namespace).
  
      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,
                   globals=None):
          """Constructor.  See class doc string."""
          self.timer = timer
          local_ns = {}
          global_ns = _globals() if globals is None else globals
          init = ''
          if isinstance(setup, str):
              # Check that the code can be compiled outside a function
              compile(setup, dummy_src_name, "exec")
              stmtprefix = setup + '\n'
              setup = reindent(setup, 4)
          elif callable(setup):
              local_ns['_setup'] = setup
              init += ', _setup=_setup'
              stmtprefix = ''
              setup = '_setup()'
          else:
              raise ValueError("setup is neither a string nor callable")
          if isinstance(stmt, str):
              # Check that the code can be compiled outside a function
              compile(stmtprefix + stmt, dummy_src_name, "exec")
              stmt = reindent(stmt, 8)
          elif callable(stmt):
              local_ns['_stmt'] = stmt
              init += ', _stmt=_stmt'
              stmt = '_stmt()'
          else:
              raise ValueError("stmt is neither a string nor callable")
          src = template.format(stmt=stmt, setup=setup, init=init)
          self.src = src  # Save for traceback display
          code = compile(src, dummy_src_name, "exec")
          exec(code, global_ns, local_ns)
          self.inner = local_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
          if self.src is not None:
              linecache.cache[dummy_src_name] = (len(self.src),
                                                 None,
                                                 self.src.split("\n"),
                                                 dummy_src_name)
          # else the source is already stored somewhere else
  
          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.
          """
          it = itertools.repeat(None, number)
          gcold = gc.isenabled()
          gc.disable()
          try:
              timing = self.inner(it, self.timer)
          finally:
              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 autorange(self, callback=None):
          """Return the number of loops and time taken so that total time >= 0.2.
  
          Calls the timeit method with *number* set to successive powers of
          ten (10, 100, 1000, ...) up to a maximum of one billion, until
          the time taken is at least 0.2 second, or the maximum is reached.
          Returns ``(number, time_taken)``.
  
          If *callback* is given and is not None, it will be called after
          each trial with two arguments: ``callback(number, time_taken)``.
          """
          for i in range(1, 10):
              number = 10**i
              time_taken = self.timeit(number)
              if callback:
                  callback(number, time_taken)
              if time_taken >= 0.2:
                  break
          return (number, time_taken)
  
  def timeit(stmt="pass", setup="pass", timer=default_timer,
             number=default_number, globals=None):
      """Convenience function to create Timer object and call timeit method."""
      return Timer(stmt, setup, timer, globals).timeit(number)
  
  def repeat(stmt="pass", setup="pass", timer=default_timer,
             repeat=default_repeat, number=default_number, globals=None):
      """Convenience function to create Timer object and call repeat method."""
      return Timer(stmt, setup, timer, globals).repeat(repeat, number)
  
  def main(args=None, *, _wrap_timer=None):
      """Main program, used when run as a script.
  
      The optional 'args' 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.
  
      '_wrap_timer' is an internal interface used for unit testing.  If it
      is not None, it must be a callable that accepts a timer function
      and returns another timer function (used for unit testing).
      """
      if args is None:
          args = sys.argv[1:]
      import getopt
      try:
          opts, args = getopt.getopt(args, "n:u:s:r:tcpvh",
                                     ["number=", "setup=", "repeat=",
                                      "time", "clock", "process",
                                      "verbose", "unit=", "help"])
      except getopt.error as 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
      time_unit = None
      units = {"usec": 1, "msec": 1e3, "sec": 1e6}
      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 ("-u", "--unit"):
              if a in units:
                  time_unit = a
              else:
                  print("Unrecognized unit. Please select usec, msec, or sec.",
                      file=sys.stderr)
                  return 2
          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 ("-p", "--process"):
              timer = time.process_time
          if o in ("-v", "--verbose"):
              if verbose:
                  precision += 1
              verbose += 1
          if o in ("-h", "--help"):
              print(__doc__, end=' ')
              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)
      if _wrap_timer is not None:
          timer = _wrap_timer(timer)
      t = Timer(stmt, setup, timer)
      if number == 0:
          # determine number so that 0.2 <= total time < 2.0
          callback = None
          if verbose:
              def callback(number, time_taken):
                  msg = "{num} loops -> {secs:.{prec}g} secs"
                  print(msg.format(num=number, secs=time_taken, prec=precision))
          try:
              number, _ = t.autorange(callback)
          except:
              t.print_exc()
              return 1
      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, end=' ')
      usec = best * 1e6 / number
      if time_unit is not None:
          scale = units[time_unit]
      else:
          scales = [(scale, unit) for unit, scale in units.items()]
          scales.sort(reverse=True)
          for scale, time_unit in scales:
              if usec >= scale:
                  break
      print("best of %d: %.*g %s per loop" % (repeat, precision,
                                              usec/scale, time_unit))
      best = min(r)
      usec = best * 1e6 / number
      worst = max(r)
      if worst >= best * 4:
          usec = worst * 1e6 / number
          import warnings
          warnings.warn_explicit(
              "The test results are likely unreliable. The worst\n"
              "time (%.*g %s) was more than four times slower than the best time." %
              (precision, usec/scale, time_unit),
               UserWarning, '', 0)
      return None
  
  if __name__ == "__main__":
      sys.exit(main())
  