CODEWITHSUNDEEP
pythontimesleep
Jamie Bull
Jamie Bull

Reputation: 13529

How much CPU should a Python time.sleep(n) call use

I have a programme running on an old laptop which is constantly monitoring a Dropbox folder for new files being added. When it's running the Python process uses close to 50% of the CPU on a dual-core machine, and about 12% on an 8-core machine which suggests it's using close to 100% of one core). This is giving off a lot of heat.

The relevant bit of code is:

while True:
    files = dict ([(f, None) for f in os.listdir(path_to_watch)])
    if len(files) > 0:
        print "You have %s new file/s!" % len(files)
        time.sleep(20)

In the case that there is no new file, surely most of the time should be spent in the time.sleep() waiting which I wouldn't have thought would be CPU-intensive - and the answers here seem to say it shouldn't be.

So two questions:

1) Since time.sleep() shouldn't be so CPU-intensive, what is going on here?

2) Is there another way of monitoring a folder for changes which would run cooler?

Upvotes: 1

Views: 404

Answers (2)

Rahul K
Rahul K

Reputation: 705

There is also a cross platform API to monitor file system changes: Watchdog

Upvotes: 2

Foon
Foon

Reputation: 6448

1) Your sleep only gets called when there are new files.

This should be much better:

while True:
    files = dict ([(f, None) for f in os.listdir(path_to_watch)])
    if len(files) > 0:
        print "You have %s new file/s!" % len(files)
    time.sleep(20)

2) Yes, especially if using linux. Gamin would be something I'd recommend looking into.

Example:

import gamin
import time
mydir = /path/to/watch
def callback(path, event):
    global mydir
    try:
        if event == gamin.GAMCreated:
            print "New file detected: %s" % (path)
            fullname = mydir + "/" + path
            print "Goint to read",fullname
            data = open(fullname).read()
            print "Going to upload",fullname
            rez = upload_file(data,path)
            print "Response from uploading was",rez
    except Exception,e: #Not good practice
        print e
        import pdb
        pdb.set_trace()


mon = gamin.WatchMonitor()
mon.watch_directory(mydir, callback)
time.sleep(1)
while True:
    ret = mon.handle_one_event()
mon.stop_watch(mydir)
del mon

Upvotes: 3

Related Questions