用于完成功能的Python装饰器

Question

Is it possible to develop a decorator to determine if a function successfully completed without crashing ? Something like the decorator below but it must detect if the function ran successfully.

def functionStartDecorator():
    print("Function has started")
    def decoratorWrapper(functionToBeDecorated):
        def wrapper(*args, **kwargs):
            #Todo log function has run
            return functionToBeDecorated(*args, **kwargs)
        return wrapper
    return decoratorWrapper  

Answer 1

As said in comments, simplest would be to wrap your function in a try/except. If your function returns nothing and simply operate by side-effect, it should be straightforward to have the decorated function return the status of that function run:

def tryfn(f):
    def decorated(*args, **kwargs):
        try:
            f(*args, **kwargs)
            return 'Ran successfully'
        except Exception as e:
            return 'Error: {}'.format(e)
    return decorated

You can then tweak the exact return type of decorated: maybe return a boolean, maybe append the status of the function to the return of f , maybe log things... The core principle will probably still be around a try/except within the decorated function. For instance, if you want to return both your return value (or None if it failed) and whether this was a success:

def tryfn(f):
    def decorated(*args, **kwargs):
        try:
            res = f(*args, **kwargs)
            return True, res
        except:
            return False, None
    return decorated

Note that in this case, you're losing the information about the exact error, so you might want to expand the return to include success, failure, error, etc... that becomes a trade-off between convenience and completeness, which will depend on your exact problem.

Answer 2

I did something like this. Do you see any issues with this code ?

def functionStartDecorator():
    def decoratorWrapper(functionToBeDecorated):
        def wrapper(*args, **kwargs):
            try:
                print("Function has started")
                result=functionToBeDecorated(*args, **kwargs)
                print("Function has complete")
                return result
            except:
                print ("Function failed")
        return wrapper
    return decoratorWrapper  

@functionStartDecorator()
def simplefunc():
    return "somthing"