Question

我有一个装饰器来注册一些类方法。如何正确获取self和run参数？

class Task(object):
    _tasks = []

    @staticmethod
    def register(name):
        def decorator(fn):
            @wraps(fn)
            def wrapper(self=None, run=True, *args, **kwargs):
                if not run:
                    task = defaultdict()
                    task['name'] = name
                    task['fn'] = getattr(self, fn.__name__, None)
                    task['obj'] = self
                    task['args'] = deepcopy(args)
                    task['kwargs'] = deepcopy(kwargs)
                    Task._tasks.append(task)
                else:
                    return fn(self, *args, **kwargs)
            return wrapper
        return decorator

class Test(object):
    def __init__(self, name):
        self.name = name

    @Task.register('foo')
    def foo(self, v1, v2):
        print 'running foo in object {} with arguments {} {}'.format(self.name, v1, v2)

    @Task.register('hello')
    def hello(self):
        print 'running hello in object {} '.format(self.name)

    def load(self):
        self.foo('1', '2', run=False)
        self.hello(run=False)

t1=Test('t1')
t1.load()

追踪（最近一次呼叫最后一次）：

TypeError: wrapper() got multiple values for keyword argument 'run'

Answer 1

你的问题与装饰者无关。以更简单的形式：你正在做的是：

def foo(run=False, *args, **kwargs):
    print(run, args, kwargs)

foo(1, 2, run=True)  # TypeError: foo() got multiple values for argument 'run'

从您的函数签名中，python将尝试设置run=1，args = (2,)，然后进入TypeError。

修复 - 尽管不是很好 - 可能是：

def foo(*args, **kwargs):
    run = kwargs.pop('run', False)  # run defaults to False; remove from kwargs
    print(run, args, kwargs)

Answer 2

run参数来自fun，所以尝试从函数的参数中获取它：

from collections import defaultdict
from copy import deepcopy
from functools import wraps

class Task(object):
    _tasks = []

    @staticmethod
    def register(name):
        def decorator(fn):
            @wraps(fn)
            def wrapper(self=None, *args, **kwargs):
                run = kwargs.pop('run', True)
                if not run:
                    task = defaultdict()
                    task['name'] = name
                    task['fn'] = getattr(self, fn.__name__, None)
                    task['obj'] = self
                    task['args'] = deepcopy(args)
                    task['kwargs'] = deepcopy(kwargs)
                    Task._tasks.append(task)
                else:
                    return fn(self, *args, **kwargs)

            return wrapper

        return decorator

Answer 3

Python3似乎有更好的参数，但不知道如何在python2中执行此操作：

from functools import wraps
def optional_debug(func):
    @wraps(func)
    def wrapper(*args, debug=False, **kwargs):
        if debug:
            print('Calling', func.__name__)
        return func(*args, **kwargs)
    return wrapper

@optional_debug
def spam(a,b,c):
    print(a,b,c)

spam(1,2,3)         # 1,2,3

spam(1,2,3, debug=True)    # Calling spam    # 1 2 3

类方法的python decorator

3 个答案: