python decorator练习

python 3.7 练习

1. 设计一个decorator，它可作用于任何函数上，并打印该函数的执行时间：

def metric(fn):
    @functools.wraps(fn)
    def wrapper(*args, **kwargs):
        begin = time.time()
        result = fn(*args, **kwargs)
        end = time.time()
        print('%s executed in %s ms' % (fn.__name__, (end - begin) * 1000))
    return wrapper


# 测试
@metric
def fast(x, y):
    time.sleep(0.0012)
    return x + y


@metric
def slow(x, y, z):
    time.sleep(0.1234)
    return x * y * z


f = fast(11, 22)
s = slow(11, 22, 33)
if f != 33:
    print('测试失败!')
elif s != 7986:
    print('测试失败!')

2. 编写一个decorator，能在函数调用的前后打印出'begin call'和'end call'的日志:

def log(x):
    def decorator(fn):
        @functools.wraps(fn)
        def wrapper(*args, **kwargs):
            print('%s %s():' % (text, fn.__name__))
            fn(*args, **kwargs)

        return wrapper
    
    if isinstance(x, str):
        text = x + ' '
        return decorator  # 若log传了str参数x，则给text赋值，并调用decorator将fn传递给decorator
    else:
        text = ''
        return decorator(x)  # 若x不是str，也就代表传递的是方法本身，则给text一个默认值，再调用decorator(x)


@log
def f():
    pass


f()
print(f.__name__)


@log('execute')
def f():
    pass


f()
print(f.__name__)

有点费脑子get✔