如何在 python 中创建装饰器 class 的不同实例

Question

I am currently trying to implement a decorator class to keep track of function calls within the waiter class that I have 2 instances of. I want the 2 waiter instances to have separate instances of the decorator class to keep track of calls on each of them, is this possible?

Code:

from functools import update_wrapper
import time

class decorater():
    """
    counts the number of calls and passes it into function
    """
    def __init__(self,func):
        self.func = func
        self.num_calls = 0
        update_wrapper(self, func)

    def __call__(self, *args, **kwargs):
        self.num_calls += 1
        result = self.func(self.num_calls, *args, **kwargs) # passes num_calls in for seconds
        print(f"total runs of {self.func.__name__}: {self.num_calls}")
        return result
    
class waiter():
    """
    waits for the number of seconds passed in
    """
    @decorater
    def wait_for(seconds, var_name):
        time.sleep(seconds)
        print(f"{var_name} waited for {seconds} seconds")

waiter1 = waiter()
waiter2 = waiter()

waiter1.wait_for("waiter1")
waiter2.wait_for("waiter2")

Output:

waiter1 waited for 1 seconds
total runs of wait_for: 1
waiter2 waited for 2 seconds
total runs of wait_for: 2

Desired output:

waiter1 waited for 1 seconds
total runs of wait_for: 1
waiter2 waited for 1 seconds
total runs of wait_for: 1

Answer 1

Decorators are not really supposed to be used how you are trying to use them, and because you are already creating multiple instances of the waiter class, why not just handle everything inside of each of those instances instead of using a decorator?

Something like this:

import time


class Waiter(object):
    """
    waits for the number of seconds passed in
    """

    def __init__(self, name):
        self.name = name
        self.num_calls = 0

    def wait(self):
        self.num_calls += 1
        print(f"total runs of {self.num_calls}")

        time.sleep(self.num_calls)
        print(f"{self.name} waited for {self.num_calls} seconds")


waiter1 = Waiter("waiter1")
waiter2 = Waiter("waiter2")

waiter1.wait()
waiter2.wait()

Output:

total runs of 1
waiter1 waited for 1 seconds
total runs of 1
waiter2 waited for 1 seconds

Answer 2

A decorator can be any callable.

In your code, you used the class decorator itself (and not an instance thereof) as the decorator. In this case, the __init__ method of the decorator class is invoked with the decorated function as an argument.

In order to use an instance of the class as a decorator, you would have to replace the decoration @decorator with @decorator() . That would cause the invocation of the __call__ method of a decorator instance with the decorated function as an argument. Of course, you would have to adapt the signature of the __call__ method.