[python] OpenCV error: the function is not implemented

I'm trying to get OpenCV working with Python on my Ubuntu machine. I've downloaded and installed OpenCV, but when I attempt to run the following python code (which should capture images from a webcam and push them to the screen)

import cv

cv.NamedWindow("w1", cv.CV_WINDOW_AUTOSIZE)
capture = cv.CaptureFromCAM(0)

def repeat():
    frame = cv.QueryFrame(capture)
    cv.ShowImage("w1", frame)
    time.sleep(10)

while True:
    repeat()

I get the following error:

The function is not implemented. Rebuild the library with Windows, GTK+ 2.x or
Carbon support. If you are on Ubuntu or Debian, install libgtk2.0-dev and
pkg-config, then re-run cmake or configure script

So I do what they ask: install the packages, move to the folder from whence I installed OpenCV, and run

sudo make uninstall
make
sudo make install

But when I try to run the python, it gives me the same error. Am I missing something?

Before installing libgtk2.0-dev and pkg-config or libqt4-dev. Make sure that you have uninstalled opencv. You can confirm this by running import cv2 on your python shell. If it fails, then install the needed packages and re-run cmake .

If you installed OpenCV using the opencv-python pip package at any point in time, be aware of the following note, taken from https://pypi.python.org/pypi/opencv-python

IMPORTANT NOTE MacOS and Linux wheels have currently some limitations:

• video related functionality is not supported (not compiled with FFmpeg)
• for example cv2.imshow() will not work (not compiled with GTK+ 2.x or Carbon support)

Also note that to install from another source, first you must remove the opencv-python package

Don't waste your time trying to resolve this issue, this was made clear by the makers themselves. Instead of cv2.imshow() use this:

img = cv2.imread('path_to_image')
plt.imshow(img, cmap = 'gray', interpolation = 'bicubic')
plt.xticks([]), plt.yticks([])  # to hide tick values on X and Y axis
plt.show()

I hope this answer is still useful, despite problem seems to be quite old.

If you have Anaconda installed, and your OpenCV does not support GTK+ (as in this case), you can simply type

conda install -c menpo opencv=2.4.11

It will install suitable OpenCV version that does not produce a mentioned error. Besides, it will reinstall previously installed OpenCV if there was one as a part of Anaconda.