使用带或不带括号的python装饰器 [英] Using python decorator with or without parentheses

问题描述

在Python中，使用带括号和不带括号的相同修饰符 有什么区别？

In Python, what is the difference between using the same decorator with and without parentheses?

例如：

不带括号：

@some_decorator
def some_method():
    pass

带括号：

@some_decorator()
def some_method():
    pass

推荐答案

some_decorator 在第一个代码段中是常规修饰符：

some_decorator in the first code snippet is a regular decorator:

@some_decorator
def some_method():
    pass

等于

some_method = some_decorator(some_method)

另一方面，第二个代码段中的 some_decorator 是可返回的可调用对象装饰者：

On the other hand, some_decorator in the second code snippet is a callable that returns a decorator:

@some_decorator()
def some_method():
    pass

等效于

some_method = some_decorator()(some_method)

正如Duncan在评论中指出的那样，某些装饰器被设计为双向工作。这是这种装饰器的一个非常基本的实现：

As pointed out by Duncan in comments, some decorators are designed to work both ways. Here's a pretty basic implementation of such decorator:

def some_decorator(arg=None):
    def decorator(func):
        def wrapper(*a, **ka):
            return func(*a, **ka)
        return wrapper

    if callable(arg):
        return decorator(arg) # return 'wrapper'
    else:
        return decorator # ... or 'decorator'

pytest.fixture 是一个更复杂的示例。

pytest.fixture is a more complex example.

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