Is there a way to control a webcam focus in pygame?

Question

I have two web cams with which I wish to take pictures. The following code accomplish that:

import pygame
import pygame.camera
from datetime import datetime
import Image
import threading
import time

class Camera (threading.Thread):
    def __init__(self, camera):
        self.camera = pygame.camera.Camera(camera,(2304,1536))
        self.stop = False
        threading.Thread.__init__(self)

    def run(self):
        self.camera.start()
        srf = self.camera.get_image()
        img = pygame.image.tostring(srf, 'RGB')
        img = Image.fromstring('RGB', srf.get_size(), img)

        img.save('%s.png'%datetime.now(), 'PNG')

s = datetime.now()

pygame.init()
pygame.camera.init()

cam1 = Camera("/dev/video0")
cam2 = Camera("/dev/video1")

cam1.start()
cam2.start()

cam1.join()
cam2.join()

print datetime.now() - s

But I need to set the focus.

I found these command lines:

apt-get install uvcdynctrl
uvcdynctrl --device=/dev/video1 --clist
uvcdynctrl --device=/dev/video1 --get='Focus, Auto'
uvcdynctrl --device=/dev/video1 --set='Focus, Auto' 0
uvcdynctrl --device=/dev/video1 --set='Focus (absolute)' 20

I though could use the following:

import os
os.system('command to set the focus')

But on my (Logitech) camera it doesn't work, and I get this output from the command line (Ubuntu 12.04, python 2.7):

uvcdynctrl --device=/dev/video1 --set='Focus, Auto' 0

[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'
[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'

Edit:

The camera is a Logitech HD Pro Webcam C920 and running:

uvcdynctrl --device=/dev/video1 --clist

Gives the output:

[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'
[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'
Listing available controls for device /dev/video1:
  Brightness
  Contrast
  Saturation
  White Balance Temperature, Auto
  Gain
  Power Line Frequency
  White Balance Temperature
  Sharpness
  Backlight Compensation
  Exposure (Absolute)
  Exposure, Auto Priority
  Pan (Absolute)
  Tilt (Absolute)
  Focus (absolute)
  Focus, Auto
  Zoom, Absolute

Answer 1

execute this

sudo apt-get install v4l-utils

and in python

os.system('v4l2-ctl -d 0 -c focus_auto=0')
os.system('v4l2-ctl -d 0 -c focus_absolute=250')