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comp.lang.python

time.time() strangeness

Nitro

2/26/2008 7:37:00 PM

Hello,

today I encountered a very odd situation. I am on Windows Vista and usin=
g =

Python 2.5.2. Here's a code snippet to illustrate my problem:

# uncomment the next line to trigger the problem
# myExtensionModule.CreateDirect3D9Device()
import time
for i in range(0,100):
print time.time()

With the line commented time.time() returns a changing value which is wh=
at =

I expect. However, when I uncomment it and create a Direct3D9 Device =

[1][2] it keeps printing the very same number over and over! In my proje=
ct =

I am using twisted which uses time.time() to schedule all calls. Since =

time.time() is completely screwed the whole application breaks.
I took a look at [3], but I can't see any obivous way how this all =

interacts. Specifically I am not sure which API time.time() uses =

internally (timeGetTime maybe?). Knowing this could probably help me deb=
ug =

more. I feel like time.time() should not break (unless the vid card =

driver/directx has a major bug). Any idea what might be happening here?
Replacing time.time() with time.clock() in twisted.python.runtime makes =
=

the problem disappear. I guess because it uses QueryPerformanceCounter.

Thanks for your time,
-Matthias

References:
[1] http://msdn2.microsoft.com/en-us/librar...(VS.85).aspx
[2] http://msdn2.microsoft.com/en-us/librar...(VS.85).aspx
[3] =

http://svn.python.org/view/python/trunk/Modules/timemodule.c?re...
&view=3Dmarkup
1 Answer

Paul Rubin

2/26/2008 7:45:00 PM

0

Nitro <nitro@dr-code.org> writes:
> With the line commented time.time() returns a changing value which is
> what I expect. However, when I uncomment it and create a Direct3D9
> Device [1][2] it keeps printing the very same number over and over!

The granularity of time.time can be quite large, maybe as much
as 1 second in some systems. Also, if the user can set the time,
the output might not be monotone. They might set the clock backwards
if it has drifted ahead, or something like that. Better to use an
explicit counter if you need a monotonically increasing sequence.