On Sat, 12 May 2007 13:51:05 -0700, Basilisk96 wrote:
> Suppose I have a function that may run for a long time - perhaps from
> several minutes to several hours. An example would be this file
> processing function:
>
> import os
> def processFiles(startDir):
> for root, dirs, files in os.walk(startDir):
> for fname in files:
> if fname.lower().endswith(".zip"):
> # ... do interesting stuff with the file here ...
>
> Imagine that there are thousands of files to process. This could take
> a while. How can I implement this so that the caller can pause or
> interrupt this function, and resume its program flow?
I don't think there really is what I would call a _clean_ way, although
people may disagree about what's clean and what isn't.
Here's a way that uses global variables, with all the disadvantages that
entails:
last_dir_completed = None
restart = object() # a unique object
def processFiles(startDir):
global last_dir_completed
if startDir is restart:
startDir = last_dir_completed
for root, dirs, files in os.walk(startDir):
for fname in files:
if fname.lower().endswith(".zip"):
# ... do interesting stuff with the file here ...
last_Dir_completed = root
Here's another way, using a class. Probably not the best way, but a way.
class DirLooper(object):
def __init__(self, startdir):
self.status = "new"
self.startdir = startdir
self.root = startdir
def run(self):
if self.status == 'new':
self.loop(self.startdir)
elif self.status == 'finished':
print "nothing to do"
else:
self.loop(self.root)
def loop(self, where):
self.status = "started"
for self.root, dirs, files in os.walk(where):
# blah blah blah...
Here's another way, catching the interrupt:
def processFiles(startDir):
try:
for root, dirs, files in os.walk(startDir):
# blah blah blah ...
except KeyboardInterrupt:
do_something_with_status()
You can fill in the details :)
As for which is "better", I think the solution using a global variable is
the worst, although it has the advantage of being easy to implement. I
think you may need to try a few different implementations and judge for
yourself.
--
Steven.
--
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