Exception Groups

Multiple exceptions can be raised at once using the ExceptionGroup class. It is a subclass of Exception which means that it cannot be used to wrap BaseExceptions.

def function_that_has_multiple_arguments(arg1, arg2, arg3, arg4):
    exceptions = []
    if arg1 is None:
        exceptions.append(ValueError("arg1 is None"))
    if arg2 is None:
        exceptions.append(TypeError("arg2 is None"))
    if arg3 is None:
        exceptions.append(ValueError("arg3 is None"))
    if arg4 is None:
        exceptions.append(OSError("arg4 is None"))
 
    if len(exceptions) > 0:
        raise ExceptionGroup(exceptions)
 
    # Code that uses arg1 and arg2
 
try:
    function_that_has_multiple_arguments(None, None, None, None)
except ExceptionGroup as e:
    for exception in e.exceptions:
        print(exception)

And if there are multiple exceptions thrown they can be unpacked and prioritized using the except* statement.

try:
    function_that_has_multiple_arguments(None, None, None, None)
except* (ValueError, TypeError) as e:
    print(f"{type(e)}, {e}")
    # Code that handles the ValueError or TypeError
except OSError as e: # This will be executed if 
    print(e)
    # Code that handles the OSError

Note: Please note that the exceptions in the ExceptionGroup must be instantiated, not just the types, this is because in practice these exceptions would have already been raised and caught by the program.

The above code will print the following:

ValueError, arg1 is None
TypeError, arg2 is None
ValueError, arg3 is None
arg4 is None