diff options
Diffstat (limited to 'Lib/timeit.py')
| -rw-r--r-- | Lib/timeit.py | 49 |
1 files changed, 25 insertions, 24 deletions
diff --git a/Lib/timeit.py b/Lib/timeit.py index 2178d52..f244b73 100644 --- a/Lib/timeit.py +++ b/Lib/timeit.py @@ -1,4 +1,4 @@ -"""Framework for measuring execution time for small code snippets. +"""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 @@ -12,7 +12,7 @@ Command line usage: Options: -n/--number N: how many times to execute 'statement' (default: see below) -r/--repeat N: how many times to repeat the timer (default 1) - -s/--setup S: statements executed once before 'statement' (default 'pass') + -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) -h/--help: print this usage message and exit @@ -20,7 +20,8 @@ Options: 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. +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. @@ -37,27 +38,23 @@ good for this. 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 (especially when comparing different versions of -Python). The baseline overhead is measured by invoking the program -without arguments. -""" - -# To use this module with older versions of Python, the dependency on -# the itertools module is easily removed; in the template, instead of -# itertools.repeat(None, number), use [None]*number. It's barely -# slower. Note: the baseline overhead, measured by the default -# invocation, differs for older 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. +be aware of it. The baseline overhead can be measured by invoking the +program without arguments. -# XXX Maybe for convenience of comparing with previous Python versions, -# itertools.repeat() should not be used at all? +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 sys import math import time -import itertools +try: + import itertools +except ImportError: + # Must be an older Python version (see timeit() below) + itertools = None __all__ = ["Timer"] @@ -75,9 +72,8 @@ else: # in Timer.__init__() depend on setup being indented 4 spaces and stmt # being indented 8 spaces. template = """ -def inner(number, timer): +def inner(seq, timer): %(setup)s - seq = itertools.repeat(None, number) t0 = timer() for i in seq: %(stmt)s @@ -126,7 +122,11 @@ class Timer: to one million. The main statement, the setup statement and the timer function to be used are passed to the constructor. """ - return self.inner(number, self.timer) + if itertools: + seq = itertools.repeat(None, number) + else: + seq = [None] * number + return self.inner(seq, self.timer) def repeat(self, repeat=default_repeat, number=default_number): """Call timer() a few times. @@ -177,13 +177,13 @@ def main(args=None): timer = default_timer stmt = "\n".join(args) or "pass" number = 0 # auto-determine - setup = "pass" + setup = [] repeat = 1 for o, a in opts: if o in ("-n", "--number"): number = int(a) if o in ("-s", "--setup"): - setup = a + setup.append(a) if o in ("-r", "--repeat"): repeat = int(a) if repeat <= 0: @@ -195,6 +195,7 @@ def main(args=None): if o in ("-h", "--help"): print __doc__, return 0 + setup = "\n".join(setup) or "pass" t = Timer(stmt, setup, timer) if number == 0: # determine number so that 0.2 <= total time < 2.0 |