try catch - Nested try statements in python?

Question

Is there a nicer way of doing the following:

try:
    a.method1()
except AttributeError:
    try:
        a.method2()
    except AttributeError:
        try:
            a.method3()
        except AttributeError:
            raise

It looks pretty nasty and I'd rather not do:

if hasattr(a, 'method1'):
    a.method1()
else if hasattr(a, 'method2'):
    a.method2()
else if hasattr(a, 'method3'):
    a.method3()
else:
    raise AttributeError

to maintain maximum efficiency.

Answer 1

A slight change to the second looks pretty nice and simple. I really doubt you'll notice any performance difference between the two, and this is a bit nicer than a nested try/excepts

def something(a):
    for methodname in ['method1', 'method2', 'method3']:
        try:
            m = getattr(a, methodname)
        except AttributeError:
            pass
        else:
            return m()
    raise AttributeError

The other very readable way is to do..

def something(a):
    try:
        return a.method1()
    except:
        pass

    try:
        return a.method2()
    except:
        pass

    try:
        return a.method3()
    except:
        pass

    raise AttributeError

While long, it's very obvious what the function is doing.. Performance really shouldn't be an issue (if a few try/except statements slow your script down noticeably, there is probably a bigger issue with the script structure)