基础知识
装饰器是可调用的对象,其参数是另一个函数(被装饰的函数).
手写装饰器
缺点:
- 不支持关键字参数
- 遮盖了被装饰函数的
__name__ 和 __doc__ 属性
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| import time
def clock(func):
def wrapper(*args):
t0 = time.perf_counter()
result = func(*args)
elapsed = time.perf_counter() - t0
name = func.__name__
arg_str = ','.join(repr(arg) for arg in args)
print(f'[%0.8fs] {name}({arg_str}) -> {result}' % (elapsed))
return result
return wrapper
@clock
def snooze(seconds):
time.sleep(seconds)
@clock
def factorial(n):
return 1 if n < 2 else n * factorial(n - 1)
if __name__ == '__main__':
print('*' * 40, 'Calling snooze(.123')
snooze(.123)
print('*' * 40, 'Calling factorial(6)')
factorial(6)
|
输出
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| **************************************** Calling snooze(.123
[0.12387697s] snooze(0.123) -> None
**************************************** Calling factorial(6)
[0.00000217s] factorial(1) -> 1
[0.00005243s] factorial(2) -> 2
[0.00015136s] factorial(3) -> 6
[0.00019293s] factorial(4) -> 24
[0.00023032s] factorial(5) -> 120
[0.00027032s] factorial(6) -> 720
|
标准库里的装饰器
functools.wraps 是标准库里的装饰器,它的作用是协助构建行为良好的装饰器,解决了手写装饰器的缺点.
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| from functools import wraps
>>> def my_decorator(f):
... @wraps(f)
... def wrapper(*args, **kwds):
... print('Calling decorated function')
... return f(*args, **kwds)
... return wrapper
|
可以调用类里面方法的装饰器
只要在参数里面加上 self, 就可以使用类里面的方法了.
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| from functools import wraps
>>> def my_decorator(f):
... @wraps(f)
... def wrapper(self, *args, **kwds):
... print('Calling decorated function')
... return f(*args, **kwds)
... return wrapper
|