我有一个循环,开头为for I,范围为(0,100)。正常情况下,它可以正常运行,但有时由于网络条件而出现故障。目前,我已经设置它,以便在失败时,它将继续在except子句中(继续到I的下一个数字)。
我是否可以将相同的数字重新分配给i,并再次运行失败的循环迭代?
我有一个循环,开头为for I,范围为(0,100)。正常情况下,它可以正常运行,但有时由于网络条件而出现故障。目前,我已经设置它,以便在失败时,它将继续在except子句中(继续到I的下一个数字)。
我是否可以将相同的数字重新分配给i,并再次运行失败的循环迭代?
当前回答
我喜欢laurent-laporte的回答。下面是我的版本,它包装在一个类与静态方法和一些例子。我实现了重试计数作为另一种重试方式。还增加了kwargs。
from typing import List
import time
class Retry:
@staticmethod
def onerror_retry(exception, callback, retries: int = 0, timeout: float = 0, timedelta: float = 0,
errors: List = None, **kwargs):
"""
@param exception: The exception to trigger retry handling with.
@param callback: The function that will potentially fail with an exception
@param retries: Optional total number of retries, regardless of timing if this threshold is met, the call will
raise the exception.
@param timeout: Optional total amount of time to do retries after which the call will raise an exception
@param timedelta: Optional amount of time to sleep in between calls
@param errors: A list to receive all the exceptions that were caught.
@param kwargs: An optional key value parameters to pass to the function to retry.
"""
for retry in Retry.__onerror_retry(exception, callback, retries, timeout, timedelta, errors, **kwargs):
if retry: retry(**kwargs) # retry will be None when all retries fail.
@staticmethod
def __onerror_retry(exception, callback, retries: int = 0, timeout: float = 0, timedelta: float = 0,
errors: List = None, **kwargs):
end_time = time.time() + timeout
continues = 0
while True:
try:
yield callback(**kwargs)
break
except exception as ex:
print(ex)
if errors:
errors.append(ex)
continues += 1
if 0 < retries < continues:
print('ran out of retries')
raise
if timeout > 0 and time.time() > end_time:
print('ran out of time')
raise
elif timedelta > 0:
time.sleep(timedelta)
err = 0
#
# sample dumb fail function
def fail_many_times(**kwargs):
global err
err += 1
max_errors = kwargs.pop('max_errors', '') or 1
if err < max_errors:
raise ValueError("I made boo boo.")
print("Successfully did something.")
#
# Example calls
try:
#
# retries with a parameter that overrides retries... just because
Retry.onerror_retry(ValueError, fail_many_times, retries=5, max_errors=3)
err = 0
#
# retries that run out of time, with 1 second sleep between retries.
Retry.onerror_retry(ValueError, fail_many_times, timeout=5, timedelta=1, max_errors=30)
except Exception as err:
print(err)
其他回答
更新2021-12-01:
自2016年6月起,不再维护重试包。 考虑使用活动的fork github.com/jd/tenacity,或者github.com/litl/backoff。
重试包是在失败时重试代码块的好方法。
例如:
@retry(wait_random_min=1000, wait_random_max=2000)
def wait_random_1_to_2_s():
print("Randomly wait 1 to 2 seconds between retries")
这里有一个快速装饰器来处理这个问题。7行,没有依赖关系。
def retry(exception=Exception, retries=3, delay=0):
def wrap(func):
for i in range(retries):
try:
return func()
except exception as e:
print(f'Retrying {func.__name__}: {i}/{retries}')
time.sleep(delay)
raise e
return wrap
@retry()
def do_something():
...
@retry(HTTPError, retries=100, delay=3)
def download_something():
...
可以添加的一个功能是扩展异常以处理多个异常(splat一个列表)。
使用递归
for i in range(100):
def do():
try:
## Network related scripts
except SpecificException as ex:
do()
do() ## invoke do() whenever required inside this loop
我喜欢laurent-laporte的回答。下面是我的版本,它包装在一个类与静态方法和一些例子。我实现了重试计数作为另一种重试方式。还增加了kwargs。
from typing import List
import time
class Retry:
@staticmethod
def onerror_retry(exception, callback, retries: int = 0, timeout: float = 0, timedelta: float = 0,
errors: List = None, **kwargs):
"""
@param exception: The exception to trigger retry handling with.
@param callback: The function that will potentially fail with an exception
@param retries: Optional total number of retries, regardless of timing if this threshold is met, the call will
raise the exception.
@param timeout: Optional total amount of time to do retries after which the call will raise an exception
@param timedelta: Optional amount of time to sleep in between calls
@param errors: A list to receive all the exceptions that were caught.
@param kwargs: An optional key value parameters to pass to the function to retry.
"""
for retry in Retry.__onerror_retry(exception, callback, retries, timeout, timedelta, errors, **kwargs):
if retry: retry(**kwargs) # retry will be None when all retries fail.
@staticmethod
def __onerror_retry(exception, callback, retries: int = 0, timeout: float = 0, timedelta: float = 0,
errors: List = None, **kwargs):
end_time = time.time() + timeout
continues = 0
while True:
try:
yield callback(**kwargs)
break
except exception as ex:
print(ex)
if errors:
errors.append(ex)
continues += 1
if 0 < retries < continues:
print('ran out of retries')
raise
if timeout > 0 and time.time() > end_time:
print('ran out of time')
raise
elif timedelta > 0:
time.sleep(timedelta)
err = 0
#
# sample dumb fail function
def fail_many_times(**kwargs):
global err
err += 1
max_errors = kwargs.pop('max_errors', '') or 1
if err < max_errors:
raise ValueError("I made boo boo.")
print("Successfully did something.")
#
# Example calls
try:
#
# retries with a parameter that overrides retries... just because
Retry.onerror_retry(ValueError, fail_many_times, retries=5, max_errors=3)
err = 0
#
# retries that run out of time, with 1 second sleep between retries.
Retry.onerror_retry(ValueError, fail_many_times, timeout=5, timedelta=1, max_errors=30)
except Exception as err:
print(err)
只有当try子句成功时才增加循环变量