On Tue, June 24, 2008 10:16 pm, Dick Moores wrote:
> At 07:00 PM 6/24/2008, Marilyn Davis wrote:
>
>
>> Has anyone ever timed the difference between using a function that was
>> imported with:
>>
>> from my_module import MyFunction
>>
>> and:
>>
>>
>> import my_module
>
> Here are 2 comparisons: <http://py77.python.pastebin.com/f53ab3769>,
> and <http://py77.python.pastebin.com/f68346b28>
>
> I don't see a significant difference.
Good. Thank you.
I'm attaching another astonishing timing result, also wrong.
It's probably always true that if a timing result is astonishing, there's
a mistake somewhere, maybe in your thinking.
This one compares using os.popen, os.listdir, and subprocess.Popen.
Marilyn Davis
>
>
> Dick
>
>
> _______________________________________________
> Tutor maillist - Tutor@python.org
> http://mail.python.org/mailman/listinfo/tutor
#!/usr/bin/env python
"""lab13_1.py -- Adding up the file sizes in the current directory,
three ways, and comparing them."""
import os
import subprocess
__pychecker__ = 'no-local'
def AccuracyTest():
print "os.listdir:", AddFilesOsListdir()
print "os.popen: ", AddFilesOsPopen()
print "subprocess:", AddFilesSubprocess()
def AddFilesOsListdir():
total = 0
files = os.listdir('.')
for f in files:
if os.path.isdir('./' + f):
continue
total += os.path.getsize('./' + f)
return total
def AddFilesOsPopen():
return TotalLsSize(os.popen("ls -al"))
def AddFilesSubprocess():
return TotalLsSize(subprocess.Popen(["ls", "-al"],
stdout=subprocess.PIPE).stdout)
def ProfileTest():
for i in range(100):
AddFilesOsListdir()
AddFilesOsPopen()
AddFilesSubprocess()
def TotalLsSize(file_obj):
total = 0
for line in file_obj:
if line[0] == 'd':
continue
parts = line.split()
if len(parts) != 9:
continue
total += int(parts[4])
return total
def main():
AccuracyTest()
import profile
profile.run('ProfileTest()')
if __name__ == '__main__':
main()
"""
$ lab13_1.py
os.listdir: 26298
os.popen: 26298
subprocess: 26298
30376 function calls in 1.872 CPU seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
101 0.004 0.000 0.004 0.000 :0(WEXITSTATUS)
101 0.012 0.000 0.012 0.000 :0(WIFEXITED)
101 0.000 0.000 0.000 0.000 :0(WIFSIGNALED)
77 0.004 0.000 0.004 0.000 :0(append)
300 0.016 0.000 0.016 0.000 :0(close)
200 0.012 0.000 0.012 0.000 :0(fcntl)
100 0.004 0.000 0.004 0.000 :0(fdopen)
100 0.068 0.001 0.068 0.001 :0(fork)
200 0.012 0.000 0.012 0.000 :0(isinstance)
5400 0.100 0.000 0.100 0.000 :0(len)
100 0.032 0.000 0.032 0.000 :0(listdir)
200 0.000 0.000 0.000 0.000 :0(pipe)
100 0.108 0.001 0.108 0.001 :0(popen)
1 0.000 0.000 0.000 0.000 :0(range)
100 0.016 0.000 0.016 0.000 :0(read)
78 0.004 0.000 0.004 0.000 :0(remove)
1 0.004 0.004 0.004 0.004 :0(setprofile)
5400 0.104 0.000 0.104 0.000 :0(split)
5300 0.236 0.000 0.236 0.000 :0(stat)
178 0.004 0.000 0.004 0.000 :0(waitpid)
1 0.000 0.000 1.868 1.868 <string>:1(<module>)
100 0.156 0.002 0.872 0.009 lab13_1.py:12(AddFilesOsListdir)
100 0.024 0.000 0.440 0.004 lab13_1.py:21(AddFilesOsPopen)
100 0.036 0.000 0.540 0.005 lab13_1.py:24(AddFilesSubprocess)
... The rest of the output is irrelevant.
It seems fishy that os.listdir() takes longer than both subprocess.Popen()
and os.popen(). Maybe somehow we are comparing apples and oranges?
$ """_______________________________________________
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
