装饰器的两种实现方式
# 利用闭包实现def function_wrapper(wrapped): @functools.wraps(wrapped)
def _wrapper(*args, **kwargs):
return wrapped(*args, **kwargs) return _wrapper @function_wrapper
def function():
pass
# 类实现class function_wrapper(object):
def __init__(self, wrapped):
self.wrapped = wrapped def __call__(self, *args, **kwargs):
return self.wrapped(*args, **kwargs) @function_wrapper
def function():
pass
# @ 带参数的情况def add_paras2_kws(*wargs,**wkws):
print ("wargs:{}".format(wargs)) print ("wkws:{}".format(wkws)) def warp_f(f): @wraps(f)
def dec(*fargs, **fkws):
print(f)
wkws.update(**fkws) print ("fargs:{}".format(fargs)) print ("fkws:{}".format(fkws)) return f(*fargs, **wkws) return dec return warp_f示例一，retry
def __retry_internal(f, exceptions=Exception, tries=-1, delay=0, max_delay=None, backoff=1, jitter=0,
logger=logging_logger):
"""
Executes a function and retries it if it failed.
:param f: the function to execute.
:param exceptions: an exception or a tuple of exceptions to catch. default: Exception.
:param tries: the maximum number of attempts. default: -1 (infinite).
:param delay: initial delay between attempts. default: 0.
:param max_delay: the maximum value of delay. default: None (no limit).
:param backoff: multiplier applied to delay between attempts. default: 1 (no backoff).
:param jitter: extra seconds added to delay between attempts. default: 0.
fixed if a number, random if a range tuple (min, max)
:param logger: logger.warning(fmt, error, delay) will be called on failed attempts.
default: retry.logging_logger. if None, logging is disabled.
:returns: the result of the f function.
"""
_tries, _delay = tries, delay while _tries: try: return f() except exceptions as e:
_tries -= 1
if not _tries: raise
if logger is not None:
logger.warning('%s, retrying in %s seconds...', e, _delay)
time.sleep(_delay)
_delay *= backoff if isinstance(jitter, tuple):
_delay += random.uniform(*jitter) else:
_delay += jitter if max_delay is not None:
_delay = min(_delay, max_delay)def retry(exceptions=Exception, tries=-1, delay=0, max_delay=None, backoff=1, jitter=0, logger=logging_logger):
"""Returns a retry decorator.
:param exceptions: an exception or a tuple of exceptions to catch. default: Exception.
:param tries: the maximum number of attempts. default: -1 (infinite).
:param delay: initial delay between attempts. default: 0.
:param max_delay: the maximum value of delay. default: None (no limit).
:param backoff: multiplier applied to delay between attempts. default: 1 (no backoff).
:param jitter: extra seconds added to delay between attempts. default: 0.
fixed if a number, random if a range tuple (min, max)
:param logger: logger.warning(fmt, error, delay) will be called on failed attempts.
default: retry.logging_logger. if None, logging is disabled.
:returns: a retry decorator.
""" @decorator
def retry_decorator(f, *fargs, **fkwargs):
args = fargs if fargs else list()
kwargs = fkwargs if fkwargs else dict() return __retry_internal(partial(f, *args, **kwargs), exceptions, tries, delay, max_delay, backoff, jitter,
logger) return retry_decoratorcomments:
__retry_internal 调用前先固定住f的参数，简化问题。
__retry_internal 要处理的只有f的调用执行。
示例二
from functools import wrapsdef return_kw(**kw):
return kwdef add_paras2_kws(*wargs,**wkws):
print ("wargs:{}".format(wargs)) print ("wkws:{}".format(wkws)) def warp_f(f): @wraps(f)
def dec(*fargs, **fkws):
print(f)
wkws.update(**fkws) print ("fargs:{}".format(fargs)) print ("fkws:{}".format(fkws)) return f(*fargs, **wkws) return dec return warp_f@add_paras2_kws(7,8,9,a=80,b=81,c=82,d=83)def test_b(*args,**kw):
return return_kw(**kw)if __name__ == '__main__':
print(test_b(1,2,3,a=4,b=5))comments：
要在常规的装饰器外再套一层接收参数，因为是先传递@的参数，接着传递被装饰的函数，再传递被装饰函数的参数。
作者：一只老梨花
链接：https://www.jianshu.com/p/44b654fc8f14
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