Question

I have code like this:

try:
    request=parse_request
except:
    print "cannot parse your malformed request"
    exit()
else:
    try:
        fh=a_factory_function()
    except:
        print "cannot create object"
    else:
        if request['operation']=='search':
            pass
        elif request['operation']=='more_like_this':
            pass
        elif request['operation']=='list_files':
            pass
        elif request['operation']=='update':
            pass
        else:
            print 'unsupported operation'

In present form it has two levels of indentation

1. parse a request
2. the factory function to generate an object to process the request

I can easily imagine this getting to 4 levels and becoming too complex for our puny reasoning. Is there a Pythonic way to flatten the indentation and make it “linear”?

Answer 1

Unless I’m misinterpreting your code, you’re using the else clause of the try statement for normal processing. In effect, you’re simulating return code error handling with exceptions. Why not do this?

try:
    request=parse_request
    fh=a_factory_function()
except MalformedRequestError:
    print "cannot parse your malformed request"
    exit()
except CreateObjectError:
    print "cannot create object"
    exit()

if request['operation']=='search':
    pass
elif request['operation']=='more_like_this':
    pass
elif request['operation']=='list_files':
    pass
elif request['operation']=='update':
    pass
else:
    print 'unsupported operation'

There is a good answer by Blair Conrad here on StackOverflow that explains why you might want to use an else clause.