Take screenshots at fixed intervals with Python using threading.Timer
I'm writing a simple GUI application with pyGTK to take desktop screenshots at fixed intervals. To schedule the shots I use the threading.Timer class and to take shots I use os.system calls to scrot.
When I click the start taking screenshots button the GlapseMain.startScreenshots method is called. When I click the stop taking screenshot button the GlapseMain.stopScreenshots method is called.
The thing is while the GTK app is working no screenshot is taken although it should. When I click the close button, it starts taking screenshots idefinitely.
Here is my code:
#!/usr/bin/env python
# -*- coding: utf8 -*-
import threading
import os
class GlapseMain:
def __init__(self):
self.outputDir = os.getenv('HOME')
self.quality = 80
self.interval = 10
self.numDigits = 15
self.currentShot = 0
def startScreenshots(self, output, quality, interval):
print 'Starting taking screenshots...'
print 'Output folder: ' + str(output)
print 'Quality: ' + str(quality)
print 'Interval: ' + str(interval)
# Update attributes
self.outputDir = output
self.quality = quality
self.interval = interval
self.currentShot = 0
# Create timer (first screenshot scheduled 1s ahead)
self.timer = threading.Timer(1.0, self._takeScreenshot)
self.timer.start()
def stopScreenshots(self):
print 'Stopped taking screenshots.'
self.timer.cancel()
def _takeScreenshot(self):
# Build scrot command
fileNumber = str(self.currentShot)
fileNumber = fileNumber.zfill(self.numDigits - len(fileNumber))
fileName = 'scr-' + fileNumber + '.jpg'
command = 'scrot -q ' + str(self.quality) + ' ' + self.outputDir + os.sep + fileName
print 'Taking screenshot: ' + command + '...'
os.system(command)
# Schedule next screenshot
self.currentShot = self.currentShot + 1
self.timer = threading.Timer(self.interval, self._takeScreenshot)
self.timer.start()
My output looks something like this:
Starting taking screenshots...
Output folder: /home/david/glapse-screens
Quality: 80.0
Interval: 2.0
Stopped taking screenshots.
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000000.jpg...
Closing gLapse...
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000001.jpg...
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000002.jpg...
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000003.jpg...
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000004.jpg...
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000005.jpg...
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000006.jpg...
Taking screenshot: scrot -q 80.0 /home/david/glapse-screens/scr-00000000000007.jpg...
Hope you could help me, thank you very much.
Edit:
I've changed the approach and now I'm using threads:
def startScreenshots(self, output, quality, interval):
print 'Starting taking screenshots...'
print 'Output folder: ' + str(output)
print 'Quality: ' + str(quality)
print 'Interval: ' + str(interval)
# Update attributes
self.outputDir = output
self.quality = quality
self.interval = interval
self.currentShot = 0
# Start a thread to take screenshots
self.done = False
self.thread = threading.Thread(target=self._takeScreenshot)
self.thread.start()
def stopScreenshots(self):
print 'Stopped taking screenshots.'
self.done = True
self.thread.join()
def _takeScreenshot(self):
# Run until we're done
while not self.done:
# Build scrot command
fileNumber = str(self.currentShot)
fileNumber = fileNumber.zfill(self.numDigits - len(fileNumber))
fileName = 'scr-' + fileNumber + '.jpg'
command = 'scrot -q ' + str(self.quality) + ' ' + self.outputDir + os.sep + fileName
print 'Taking screenshot: ' + command + '...'
os.system(command)
# Schedule next screenshot
print 'Scheduling next screenshot...'
self.currentShot = self.currentShot + 1
time.sleep(self.interval)
It prints the message but not executes the os.system instruction until I press the stop button.
To response:
You also need to call
gtk.gdk.threads_init()
before gtk.main() is called if you want threads with gtk
Let _takeScreenshot() have a while loop instead and do not start a new thread for the next screenshot. You already have a worker thread for this, eg
You also need a Thread instead of a Timer
def _takeScreenshot(self):
while self.notDone:
# take screen shot
# ..
time.sleep(self.interval)
Then in your cancel method do something like:
def stopScreenshots(self):
self.notDone = False
self.timer.join() # wait for thread to finish