[Python-Dev] Startup time (original) (raw)

Jeff Epler jepler@unpythonic.net
Wed, 7 May 2003 19:53:44 -0500

On Wed, May 07, 2003 at 07:55:03PM -0400, Raymond Hettinger wrote:

I don't think timeit.py helps here. It works by substituting both the setup and statement inside a compiled function.

So, none of the above timings show the effect of a top level import versus one that is inside a function. It does compare 1 deep nesting to 2 levels deep.

This program prints clock() times for 4e6 imports, first at global and then at function scope. Function scope wins a little bit, possibly due to the speed of STORE_FAST instead of STORE_GLOBAL (or would it be STORE_NAME?)

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(on a different machine than my earlier timeit results, running 2.2.2)

time for global import 30.21

time for function import 27.31

import time, sys

t0 = time.clock() for i in range(1e6): import sys; import sys; import sys; import sys; t1 = time.clock()

print "time for global import", t1-t0

def f(): for i in range(1e6): import sys; import sys; import sys; import sys;

t0 = time.clock() f() t1 = time.clock() print "time for function import", t1-t0 ########################################################################

If Skip is thinking of a slowdown for import and function scope, could it be the {LOAD,STORE}_FAST performance killer 'import *'? (wow, LOAD_NAME isn't as much slower than LOAD_FAST as you might expect..)

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time for <function f at 0x816306c> 27.9

time for <function g at 0x8159e9c> 37.94

import new, sys, time m = new.module('m') sys.modules['m'] = m m.dict.update({'all': ['x'], 'x': None})

def f(): from m import x x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x

def g(): from m import * x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x x; x; x; x; x; x; x; x; x; x

for fn in f, g: t0 = time.clock() for i in range(1e6): fn() t1 = time.clock() print "time for", fn, t1-t0 ########################################################################