picamera2 library basics in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Picamera2 preview code?

Consider this Python code using the picamera2 library on a Raspberry Pi. What will it print when run?

Raspberry Pi

from picamera2 import Picamera2
picam2 = Picamera2()
picam2.start_preview()
print('Preview started')

A Preview started

B Error: start_preview() is not a function

C Nothing is printed

D Preview started\nCamera error

💡 Hint

The start_preview() method starts the camera preview and does not block the program.

The code initializes the camera and starts the preview. Then it prints 'Preview started'. No errors occur.

❓ Predict Output

intermediate

What does this code print after capturing an image?

This code captures an image and prints the type of the image data. What is printed?

Raspberry Pi

from picamera2 import Picamera2
picam2 = Picamera2()
picam2.start()
image = picam2.capture_array()
print(type(image))

A <class 'bytes'>

B <class 'numpy.ndarray'>

C <class 'PIL.Image.Image'>

D Error: capture_array() not found

💡 Hint

capture_array() returns image data as a numpy array.

The capture_array() method returns the image as a numpy array, so printing its type shows .

🔧 Debug

advanced

Why does this Picamera2 code raise an error?

This code tries to capture an image without starting the camera. What error will it raise?

Raspberry Pi

from picamera2 import Picamera2
picam2 = Picamera2()
image = picam2.capture_array()
print('Captured')

A RuntimeError: Camera not started

B AttributeError: 'Picamera2' object has no attribute 'capture_array'

C SyntaxError: missing parentheses

D No error, prints 'Captured'

💡 Hint

You must start the camera before capturing images.

Calling capture_array() before starting the camera causes a RuntimeError because the camera hardware is not active.

🧠 Conceptual

advanced

What is the purpose of the Picamera2.start_preview() method?

Choose the best description of what start_preview() does in the picamera2 library.

A It stops the camera preview and releases resources.

B It captures a still image and saves it to disk.

C It initializes the camera hardware but does not show anything.

D It starts showing a live camera preview on the screen.

💡 Hint

Think about what 'preview' means in a camera context.

start_preview() opens a window or display area showing the live camera feed so you can see what the camera sees.

❓ Predict Output

expert

What is the output of this Picamera2 exposure mode code?

This code sets the exposure mode and prints the current mode. What will it print?

Raspberry Pi

from picamera2 import Picamera2
picam2 = Picamera2()
picam2.start()
picam2.set_controls({'ExposureMode': 1})
print(picam2.controls.get('ExposureMode', 'default'))

A Error: set_controls() not supported

B default

C 1

D None

💡 Hint

set_controls() changes camera settings; controls is a dictionary of current settings.

After setting ExposureMode to 1 ('night'), reading it from controls returns 1.