如果没有引发异常，您如何以Python方式告诉程序始终执行某些操作

Question

Say I have a setup like this

def add(self, value):

    self._length += 1

    if isinstance(value, str):
        if '\n' in value:
            return self.func_a(value)
        return self.func_b(value)
    return self.func_c(value)

As you can see, many return statements. Each return statement with its respective function call.

Whenever the chosen function (out of func_a , func_b and func_c ) runs successfully we want _length to get incremented and the return value of the function to get returned.

But if the chosen function doesn't run successfully we want _length to stay the same.

Obviously, in the code I have shown above _length will get incremented no matter what.

I took the following approach

def add(self, value):

    if isinstance(value, str):
        if '\n' in value:
            rt = self.func_a(value)
        else:
           rt = self.func_b(value)
    else:
        rt = self.func_c(value)



    self._length += 1
    return rt

which works but it is rather ugly.

Is there a more pythonic approach to this?

Answer 1

If you know which exceptions may be raised, you can do something like the following:

if isinstance(value, str):
    fn = self.func_a if '\n' in value else self.func_b
else:
    fn = self.func_c


try:
    rt = fn(value)
except Exception as e:
    # We encountered an error
else:
    self._length += 1
finally:
    # We want to always run this code

Answer 2

'chosen function doesn't run successfully' is opaque. If a chosen function raises an error, the entire process will be stopped. Anyway, both codes mentioned work the same.