如何在循环内定义 Python 函数并使用 *args 和 **kwargs

Question

I'm trying to print a message when instance methods get called, like below. I'm running into this problem , but I'm having trouble solving it in my case because all the solutions seem to require passing in specific arguments which I can't do here.

class MathLab:
    def add(self, a, b):
        print(a + b)

    def mult(self, a, b):
        print(a * b)


m = MathLab()

for method in [m.add, m.mult]:
    def tracked_method(*args, **kwargs):
        print("Running: " + method.__name__)
        method(*args, **kwargs)


    m.__setattr__(method.__name__, tracked_method)

m.add(5, 5)

Output

Running: mult
25

Answer 1

Would this help? Add a keyword argument with a default value in order to do early binding of method (then use that keyword argument _method in place of method inside the function).

The whole code is shown for convenience, but the only part changed from the code in the question is the tracked_method function itself.

class MathLab:
    def add(self, a, b):
        print(a + b)

    def mult(self, a, b):
        print(a * b)


m = MathLab()

for method in [m.add, m.mult]:
    def tracked_method(*args, _method=method, **kwargs):
        print("Running: " + _method.__name__)
        _method(*args, **kwargs)


    m.__setattr__(method.__name__, tracked_method)

m.add(5, 5)

Gives:

Running: add
10

By the way, instead of using m.__setattr__(...) , you could simply use setattr(m, ...) .