PiCamera, PIR Motion Sensor 'Attribute Error: __exit__'

Question

I'm pretty new to both Python and utilizing the GPIO pins on my Raspberry Pi. I am trying to make a "trail camera" that will take pictures of birds when they land on the branches of the trees just off of my back porch.

I have a PIR motion sensor and the camera module hooked up. I have written the following script, largely copied from here, to have the motion sensor wait for motion, then take a photograph, then reset to waiting for the next bit of motion.

import picamera
from datetime import datetime
from time import sleep
from gpiozero import MotionSensor


pir = MotionSensor(17)

def generate_filename():
    timestampe = datetime.strftime(datetime.now(), "%Y-%m-%d-%H-%M-%S-%f")
    filename = 'home/pi/trail_cam_photos/photo_%s' % timestamp
    return filename

while True:
    pir.wait_for_motion()
    while pir.motion_detected:
        with picamera.PiCamera as camera:
            camera.resolution=(1024, 768)
            camera.start_preview()
            camera.sleep(2)
            file = generate_filename
            camera.capture(file)
            camera.stop_preview()
            file.close()

When I run the script and then wave my hand over the PIR sensor, I get the following error:

Traceback (most recent call last):
  File "trail_cam.py", line 19, in <module>
    with picamera.PiCamera as camera:
AttributeError: __exit__

What can cause this error?

Answer 1

The error:

AttributeError: __exit__

indicates that the object is not a context manager. In this particular case it is because picamera.PiCamera is a class not an instance of a class. The proper usage to use this class as a context manager would be:

with picamera.PiCamera() as camera:

Note the addition of the (). This instantiates a PiCamera and then the context manager should work as expected.