13. API - Exceptions

All exceptions defined by picamera are listed in this section. All exception classes utilize multiple inheritance in order to make testing for exception types more intuitive. For example, PiCameraValueError derives from both PiCameraError and ValueError. Hence it will be caught by blocks intended to catch any error specific to the picamera library:

try:
    camera.brightness = int(some_user_value)
except PiCameraError:
    print('Something went wrong with the camera')

Or by blocks intended to catch value errors:

try:
    camera.contrast = int(some_user_value)
except ValueError:
    print('Invalid value')

13.1. Warnings

exception picamera.PiCameraWarning

Bases: Warning

Base class for PiCamera warnings.

exception picamera.PiCameraDeprecated

Bases: picamera.exc.PiCameraWarning, DeprecationWarning

Raised when deprecated functionality in picamera is used.

exception picamera.PiCameraFallback

Bases: picamera.exc.PiCameraWarning, RuntimeWarning

Raised when picamera has to fallback on old functionality.

exception picamera.PiCameraResizerEncoding

Bases: picamera.exc.PiCameraWarning, RuntimeWarning

Raised when picamera uses a resizer purely for encoding purposes.

exception picamera.PiCameraAlphaStripping

Bases: picamera.exc.PiCameraWarning, RuntimeWarning

Raised when picamera does alpha-byte stripping.

13.2. Exceptions

exception picamera.PiCameraError

Bases: Exception

Base class for PiCamera errors.

exception picamera.PiCameraValueError

Bases: picamera.exc.PiCameraError, ValueError

Raised when an invalid value is fed to a PiCamera object.

exception picamera.PiCameraRuntimeError

Bases: picamera.exc.PiCameraError, RuntimeError

Raised when an invalid sequence of operations is attempted with a PiCamera object.

exception picamera.PiCameraClosed

Bases: picamera.exc.PiCameraRuntimeError

Raised when a method is called on a camera which has already been closed.

exception picamera.PiCameraNotRecording

Bases: picamera.exc.PiCameraRuntimeError

Raised when stop_recording() or split_recording() are called against a port which has no recording active.

exception picamera.PiCameraAlreadyRecording

Bases: picamera.exc.PiCameraRuntimeError

Raised when start_recording() or record_sequence() are called against a port which already has an active recording.

exception picamera.PiCameraMMALError(status, prefix='')

Bases: picamera.exc.PiCameraError

Raised when an MMAL operation fails for whatever reason.

exception picamera.PiCameraPortDisabled(msg)

Bases: picamera.exc.PiCameraMMALError

Raised when attempting a buffer operation on a disabled port.

This exception is intended for the common use-case of attempting to get or send a buffer just when a component is shutting down (e.g. at script teardown) and simplifies the trivial response (ignore the error and shut down quietly). For example:

def _callback(self, port, buf):
    try:
        buf = self.outputs[0].get_buffer(False)
    except PiCameraPortDisabled:
        return True # shutting down
    # ...

13.3. Functions

picamera.mmal_check(status, prefix='')

Checks the return status of an mmal call and raises an exception on failure.

The status parameter is the result of an MMAL call. If status is anything other than MMAL_SUCCESS, a PiCameraMMALError exception is raised. The optional prefix parameter specifies a prefix message to place at the start of the exception’s message to provide some context.