Exceptions: A metaphor

Concept of Raising Exceptions and Handling Exceptions

• Metaphor: Welder and Welding Pipes

  • Task of the Welder: Welding pipes is the primary responsibility of the welder.

  • Normal Operation:

    • The welder continues to work until an issue arises.

    • They are actively trying to weld the pipes.

Handling Issues During Welding

• Issues May Arise: When problems occur, the welder must stop to handle them.

  • Planned Issues:

    • The welder identifies known problems and has specific plans to address them.

    • Examples of Planned Issues:

      • Melted metal is dripping: The welder stops to wipe it off.

      • Broken electrode: The welder replaces it immediately.

• Unplanned Issues:

  • New problems not anticipated must be dealt with differently.

    • Example of an Unplanned Issue:

      • Welding too hard may result in a hole in the pipe.

      • This issue was not planned for, leaving the welder unsure of how to proceed.

      • The welder calls the supervisor for assistance with this unplanned issue.

Relation to Python Exception Handling

• Executing a Method: When a method is running in Python, it can encounter exceptions.

• Execution Stops:

  • Similar to the welder stopping work, code execution halts when an exception occurs.

  • The exception must be handled to continue execution.

• Handling Exceptions:

  • If the method can handle the exception on the spot, normal execution resumes.

  • If the method does not handle it, the exception is passed to the method that invoked it (the calling method).

• Calling Stack:

  • Each method is part of a calling stack.

  • When an exception occurs, it bubbles up from the current method to its caller until it is handled or the program crashes.

    • If a caller can handle the exception, it takes care of it.

    • If no method can handle it, the program terminates.