4

在 PEP 3107 和这个 SO 答案中，暗示 Python3K 函数注释和装饰器适合手和手套——我应该能够编写一个与函数属性一起使用的装饰器。

但是，我无法弄清楚如何使它们按我的预期工作。

考虑：

def verbose(lcls):
    def wrap(f):
        print('inside wrap')
        def wf(*args):
            print('inside wf')
            print('lcls in wf:',lcls)
            print('locals in wf:',locals())
            print('wf annotations:',wf.__annotations__)
            print('xYx annotations:',xXy.__annotations__)
            r=f(*args)
            print('after f(*args)')
            return r
        return wf
    return wrap           

@verbose(locals())    
def xXy(x: 'x in x\'s', y: 'y in Y\'s') -> ('x times y','in x and y units'):
    print('locals in xXy:',locals())
    return x*y

xy=xXy(10,3)    
print(xy)

印刷：

inside wrap
inside wf
lcls in wf: {'xXy': <function verbose.<locals>.wrap.<locals>.wf at 0x109767ef0>, '__doc__': None, 'verbose': <function verbose at 0x109767050>, '__cached__': None, '__builtins__': <module 'builtins'>, '__package__': None, '__file__': '/private/var/folders/gx/gqtmx9mn7b75pk1gfy0m9w3w0000gp/T/Cleanup At Startup/test-383453350.857.txt', '__loader__': <_frozen_importlib.SourceFileLoader object at 0x10959ac10>, '__name__': '__main__'} 
locals in wf: {'f': <function xXy at 0x109767e60>, 'args': (10, 3), 'lcls': {'xXy': <function verbose.<locals>.wrap.<locals>.wf at 0x109767ef0>, '__doc__': None, 'verbose': <function verbose at 0x109767050>, '__cached__': None, '__builtins__': <module 'builtins'>, '__package__': None, '__file__': '/private/var/folders/gx/gqtmx9mn7b75pk1gfy0m9w3w0000gp/T/Cleanup At Startup/test-383453350.857.txt', '__loader__': <_frozen_importlib.SourceFileLoader object at 0x10959ac10>, '__name__': '__main__'}, 'wf': <function verbose.<locals>.wrap.<locals>.wf at 0x109767ef0>}
wf annotations: {}
xYx annotations: {}
locals in xXy: {'y': 3, 'x': 10}
after f(*args)
30

那组行告诉我的是，我看不到如何在装饰器中访问 xXy 中的 x 和 y 的值或 xXy 的函数属性。

我想做的是1）有一个带有PEP 3107中指定的注释的函数，2）能够有一个装饰器，可以访问函数注释和调用函数的值，而不仅仅是xXy的克隆函数签名。

4

2 回答 2

4

我相信您正在寻找functools.wraps()：

def verbose(lcls):
    def wrap(f):
        print('inside wrap')
        @functools.wraps(f)
        def wf(*args):
            print('inside wf')
            print('lcls in wf:',lcls)
            print('locals in wf:',locals())
            print('wf annotations:',wf.__annotations__)
            print('xYx annotations:',xXy.__annotations__)
            r=f(*args)
            print('after f(*args)')
            return r
        return wf
    return wrap

这是一个简单的装饰器，可确保包装函数携带它包装的函数的属性。

于 2013-02-25T02:59:43.360 回答
4

3.3 版中的新功能，inspect.signature()将允许您在函数装饰器中获得所需的信息。这是一个使用它来打印在每次调用装饰函数时传递的参数名称和值以及访问相关注释的示例：

import functools
import inspect

def verbose(wrapped):
    @functools.wraps(wrapped)  # optional - make wrapper look like wrapped
    def wrapper(*args):
        print('inside wrapper:')
        fsig = inspect.signature(wrapped)
        parameters = ', '.join('{}={}'.format(*pair)
                               for pair in zip(fsig.parameters, args))
        print('  wrapped call to {}({})'.format(wrapped.__name__, parameters))
        for parameter in fsig.parameters.values():
            print("  {} param's annotation: {!r}".format(parameter.name,
                                                         parameter.annotation))
        result = wrapped(*args)
        print('  returning {!r} with annotation: {!r}'.format(result,
                                                         fsig.return_annotation))
        return result
    return wrapper

@verbose
def xXy(x: 'x in X\'s', y: 'y in Y\'s') -> ('x times y','in X and Y units'):
    return x*y

xy = xXy(10, 3)
print('xXy(10, 3) -> {!r}'.format(xy))

输出：

inside wrapper:
  wrapped call to xXy(x=10, y=3)
  x param's annotation: "x in X's"
  y param's annotation: "y in Y's"
  returning 30 with annotation: ('x times y', 'in X and Y units')
xXy(10, 3) -> 30
于 2013-02-25T04:46:39.110 回答