write to log file

[Hans Nowak]

Tom wrote:
> Hi,
> I have a log file and of course I want to add the new information to the 
> end of that log file. Unfortunately I always delete the old information 
> and only append the current info.
> 
> Right now I do it like this:
> I call a module which consists of a class and a function. It actually 
> doesn't matter, but I just included it for the sake of completeness.
> The module looks like this:
> 
> class log_C:
>   def errorlog(self, filename, Data, d):
>       LogFile = file(filename, 'w')
>       ErrorInfo = Data[d+1]
>       LogFile.write(ErrorInfo)
>       LogFile.close()
> 
> How can I add the new info without deleting the old info?
> I tried the modes 'a' and 'a+' but they both didn't work. Actually the 
> data was totally unreadable! It was kind of messed up. I don't know why.

The following works for me:

 >>> f = open('c:/temp/test.txt', 'w')
 >>> for x in ('fee', 'fi', 'fum', 'fo'):
...     print >> f, x
...
 >>> f.close()
 >>> g = open('c:/temp/test.txt', 'a+r')
 >>> print >> g, 'slag-blah'
 >>> g.close()
 >>> file('c:/temp/test.txt').readlines()
['fee\n', 'fi\n', 'fum\n', 'fo\n', 'slag-blah\n']

HTH,

-- 
Hans (hans at zephyrfalcon.org)
http://zephyrfalcon.org/