In case if you are detect QR codes from video stream or something else, creating all required structures for each frame is very expensive. In that case you can operate Low-level API (TODO: Link) or use quirc.Decoder.
Create new decoder and supply to it frame’ width and height: quirc.Decoder(640, 480).
For each frame call decoder method decode() and apply to it raw pixels binary data.
Attention! Streaming decoder suppress quirc.DecodeException, because if current frame cannot be decoded, it must not crash a program.
import quirc # Create new decoder with frame size decoder = quirc.Decoder(640, 480) while True: # Use OpenCV or something else here # In this example, here is a pseudo-code image = get_new_frame_from_camera() # Convert it to the grayscale, so each byte will represent one pixel image.convert('grayscale') for code in decoder.raw(image.to_string()): print code.text