Why Are Bare `except` Blocks in Python a Bad Idea?

The Pitfalls of Bare 'except' Blocks

When creating a function to check for the presence of an image on the screen using PyAutoGUI, a common approach is to employ an 'except' block to handle potential exceptions. However, PyCharm warns against leaving the 'except' bare, prompting the question: what's the downside?

Risks of Bare 'except'

Bare 'except' blocks, which do not specify a specific exception type, can lead to unexpected consequences:

• Masking Exceptional Behavior: They indiscriminately catch all exceptions, including KeyboardInterrupt (user interruption) and Python-raised errors like SystemExit. This can obscure critical events and prevent appropriate handling.
• Unrecoverable Failures: Unknown failures are typically unrecoverable, and suppressing them can lead to unexpected program behavior and data loss.

Best Practices: Targeted Exception Handling

To mitigate these risks, it's crucial to specify the specific exceptions you're expecting. In this case, the expected error is pyautogui.ImageNotFoundException, indicating that the image could not be located on the screen. The revised code should handle this exception explicitly:

def check_image_on_screen(image):
    try:
        pyautogui.locateCenterOnScreen(image)
        return True
    except pyautogui.ImageNotFoundException:
        return False

By identifying the specific exception, you enable targeted error handling, allowing the program to gracefully handle only the expected failures while delegating unknown errors to the interpreter for appropriate action.

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