前一段时间,我需要R中的retry
函数来处理服务器响应缓慢。该函数将具有以下行为:(尝试操作(函数或方法),如果失败,请稍等片刻然后重试)x10
我想到了以下内容:
retry <- function(fun, max_trys = 10, init = 0){
suppressWarnings(tryCatch({
Sys.sleep(0.3);
if(init<max_trys) {fun}
}, error=function(e){retry(fun, max_trys, init = init+1)}))}
效果很好。现在我在Python3中需要相同的代码,因此我尝试制作相同的代码:
import time
def retry_fun(fun, max_trys = 10, init=0):
try:
time.sleep(0.3)
if(init<max_trys):
fun
except:
retry_fun(fun, max_trys, init = init+1)
但是当我运行它时,它使我的内核崩溃。因为我是Python的初学者,所以我不确定导致崩溃的原因以及是否/如何将函数作为参数传递给另一个函数。
你能帮帮我吗?
除了能够传递函数并通过在名称后添加()
(调用调用的Python语法)来使用它们之外,您[[不需要需要使用递归;只需将其循环:
import time
def retry(fun, max_tries=10):
for i in range(max_tries):
try:
time.sleep(0.3)
fun()
break
except Exception:
continue
except Exception
应该更改为捕获该函数可能引发的有意义的异常。使用Exception
(就像我在示例中所做的那样)通常是不好的做法,因为它会捕获大量的异常,而这些异常可能是您不想捕获的。除此之外,使用
for-loop
而不是显式的第三计数器和递归(对于较大的值,这会导致较长的调用堆栈)更好。
def retry_call(function_name, args=None, kwargs=None, retries=3):
pass_on_args = args if args else []
pass_on_kwargs = kwargs if kwargs else {}
for index in range(1, retries+1):
try:
return function_name(*pass_on_args, **pass_on_kwargs)
except Exception as error:
if index == retries:
LOGGER.error("Failed %s attempts at calling: %s", retries, function_name)
LOGGER.error(" args: %s", args)
LOGGER.error(" kwargs: %s", kwargs)
LOGGER.error(" error: %s", error)
raise
else:
LOGGER.warning("Failed %d attempt(s) at calling: %s", index, function_name)
LOGGER.warning("Retrying")
def get_variable
with open(FILE) as info:
for line in info:
if 'Mode' in line:
return mode
然后您将调用该函数:
mode = retry(get_variable) print(mode)
retry
装饰器,该装饰器将在发生异常时重试。此外,您还可以设置自定义指数延迟。文档字符串说明了如何使用装饰器。在这里,您去:import logging
import time
from functools import partial, wraps
def retry(func=None, exception=Exception, n_tries=5, delay=5, backoff=1, logger=False):
"""Retry decorator with exponential backoff.
Parameters
----------
func : typing.Callable, optional
Callable on which the decorator is applied, by default None
exception : Exception or tuple of Exceptions, optional
Exception(s) that invoke retry, by default Exception
n_tries : int, optional
Number of tries before giving up, by default 5
delay : int, optional
Initial delay between retries in seconds, by default 5
backoff : int, optional
Backoff multiplier e.g. value of 2 will double the delay, by default 1
logger : bool, optional
Option to log or print, by default False
Returns
-------
typing.Callable
Decorated callable that calls itself when exception(s) occur.
Examples
--------
>>> import random
>>> @retry(exception=Exception, n_tries=4)
... def test_random(text):
... x = random.random()
... if x < 0.5:
... raise Exception("Fail")
... else:
... print("Success: ", text)
>>> test_random("It works!")
"""
if func is None:
return partial(
retry,
exception=exception,
n_tries=n_tries,
delay=delay,
backoff=backoff,
logger=logger,
)
@wraps(func)
def wrapper(*args, **kwargs):
ntries, ndelay = n_tries, delay
while ntries > 1:
try:
return func(*args, **kwargs)
except exception as e:
msg = f"{str(e)}, Retrying in {ndelay} seconds..."
if logger:
logging.warning(msg)
else:
print(msg)
time.sleep(ndelay)
ntries -= 1
ndelay *= backoff
return func(*args, **kwargs)
return wrapper