Do I need a return statement after a Python exception?

Question

I'm rather new to python, and I want to make sure I'm doing this correctly. I'd like to have an exception class:

class UnknownCommandReceived(Exception):
    def __init__(self, value):
        self.value = value

    def __str__(self):
        return repr(self.value)

I will raise the exception at the end of this function if no regexes match:

def cmdType(self):
    match = re.match(r'(<[ \w]+>),\s*(\d+)?,?\s*(\d+)?', cmd, re.IGNORECASE)
    if match: 
        cmd_type = 'int_tool'
        return cmd_type, match

    match = re.match(r'LCD\(([^\)]*)\)?_?(RED|YELLOW|GREEN|TEAL|BLUE|VIOLET|OFF|ON|SELECT|LEFT|DOWN|RIGHT)?', cmd, re.IGNORECASE)
    if match: 
        cmd_type = 'lcd'
        return cmd_type, match

    match = re.match(r'buffer(_read|_num|_line)(\((\w)\))?', cmd, re.IGNORECASE)
    if match: 
        cmd_type = 'buffer'
        return cmd_type, match

    # ... More regex matches ... 

    raise UnknownCommandReceived( "cmdType received an unknown command" )

    # unecessary return?
    return 'None', None

My question is--if the exception is always raised, then do I not need a return statement at the end of the function? My apologies.. its a very basic question. My understanding is that an exception once an exception is raised, execution will never return to that point of the code (unless its a loop, or a function that is called again). It will go straight to the catch and continue from there?

Your understanding is correct.

Mark Amery
– Mark Amery

2013-05-18 08:34:51 +00:00
Commented May 18, 2013 at 8:34 — Mark Amery
– Mark Amery, Commented May 18, 2013 at 8:34

shx2 · Accepted Answer · 2013-05-18 08:33:57Z

16

No you don't. The return statement is unreachable.

Also, static-analysis tools, such as pyflakes will report that as an error.

answered May 18, 2013 at 8:33

shx2

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