如何在try / catch中自动包装函数调用？

Question

I have a lot of getter functions like this:

get_property_a(default=None):
  try:
     self.data.get("field_1")[0].get("a")
  except Exception as e:
     return default

get_property_b(default=None):
  try:
     self.data.get("field_2")[0].get("b")
  except Exception as e:
     return default

...

Is there a way to not wrapping all the getters in try/except? It would be nice if it is some kind of annotation like this:

@silent_exec(default=None)
def get_property_b():
  self.data.get("field_2")[0].get("b")

Thanks

Answer 1

You can do this by writing your own decorator:

import functools

def silent_exec(default=None):
    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            try:
                return func(*args, **kwargs):
            except Exception:
                return default
        return wrapper
    return decorator

With that said, I'd be very wary of using this. You should very rarely be catching all exceptions (as we've done here). Normally you it's better to specify a tuple of exceptions that you actually expect and know how to handle...

import functools

def silent_exec(exceptions, default=None):
    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            try:
                return func(*args, **kwargs):
            except exceptions:
                return default
        return wrapper
    return decorator

@silent_exec((IndexError, KeyError), default=None)
def get_property_b():
  self.data.get("field_2")[0].get("b")

This way, you don't end up catching/silencing programming errors -- those will still get raised, you can look at them in the logs or wherever they get reported and you can go back in and fix them.