get the size of a dynamically changing file fast ?

[Stef Mientki]

Mike Driscoll wrote:
> On Jan 22, 3:35 pm, Stef Mientki <stef.mien... at gmail.com> wrote:
>   
>> Mike Driscoll wrote:
>>     
>>> On Jan 17, 3:56 pm, Stef Mientki <stef.mien... at gmail.com> wrote:
>>>       
>>>> hello,
>>>>         
>>>> I've a program (not written in Python) that generates a few thousands
>>>> bytes per second,
>>>> these files are dumped in 2 buffers (files), at in interval time of 50 msec,
>>>> the files can be read by another program, to do further processing.
>>>>         
>>>> A program written in VB or delphi can handle the data in the 2 buffers
>>>> perfectly.
>>>> Sometimes Python is also able to process the data correctly,
>>>> but often it can't :-(
>>>>         
>>>> I keep one of the files open en test the size of the open datafile each
>>>> 50 msec.
>>>> I have tried
>>>>     os.stat ( ....) [ ST_SIZE]
>>>>     os.path.getsize ( ... )
>>>> but they both have the same behaviour, sometimes it works, and the data
>>>> is collected each 50 .. 100 msec,
>>>> sometimes 1 .. 1.5 seconds is needed to detect a change in filesize.
>>>>         
>>>> I'm using python 2.4 on winXP.
>>>>         
>>>> Is there a solution for this problem ?
>>>>         
>>>> thanks,
>>>> Stef Mientki
>>>>         
>>> Tim Golden has a method to watch for changes in a directory on his
>>> website:
>>>       
>>> http://tgolden.sc.sabren.com/python/win32_how_do_i/watch_directory_fo...
>>>       
>>> This old post also mentions something similar:
>>>       
>>> http://mail.python.org/pipermail/python-list/2007-October/463065.html
>>>       
>>> And here's a cookbook recipe that claims to do it as well using
>>> decorators:
>>>       
>>> http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/426620
>>>       
>>> Hopefully that will get you going.
>>>       
>>> Mike
>>>       
>> thanks Mike,
>> sorry for the late reaction.
>> I've it working perfect now.
>> After all, os.stat works perfectly well,
>> the problem was in the program that generated the file with increasing
>> size,
>> by truncating it after each block write, it apperently garantees that
>> the file is flushed to disk and all problems are solved.
>>
>> cheers,
>> Stef Mientki
>>     
>
> I almost asked if you were making sure you had flushed the data to the
> file...oh well.
>   
Yes, that's a small disadavantage of using a "high-level" language,
where there's no flush available, and you assume it'll done 
automatically ;-)

cheers,
Stef