Handling errors as return values

• Each function that fails returns some error indicator. None ? An object that has and attribute "error"?
• None would be bad as that cannot indicate different errors.
• Every called needs to check if the function returned error. If at any point we forget our system might run with hidden failures.

def some_function()
    result = do_something(filename)
    if result:
        do_something_else(result)
    else:
        return result

main()
    ...
    result = some_function()

• If we forget to check the result and pass it on, we might get some error in the code that is quite far from where the error actually happened

main()
    ...
    result = do_something(filename)
    ...
    ...
    do_something_else(result)

• This can happen even if we don't pass the result around:

main()
    ...
    do_something(filename)
    ...
    ...
    do_something_else_assuming_the_other_worked()