重试运行函数的Pythonic方式 [英] Pythonic way of retry running a function

问题描述

Python专业人员如何重试运行将请求Web服务的功能（Web服务有时会失败）

How a Python Professinal would retry running a function that will request a web service(the webservice sometimes fails)

该功能：

def some_request(uri):
    try:
        req = requests.post('http://someuri.com', {'test': 'yes'})
    except Exception as e:
        return False
    return {'id': req.json()['value'], 'other': req.json()['other']}

您使用一会儿还是其他python惯用语来处理重试？

You handle the retry with a while or other python idiom?

为我提供了正确方法的线索。

Give me a clue on how to do it the right way.

推荐答案

定义重试实用程序：

# Retry utility   
# set logging for `retry` channel
import logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger('retry')

# Define Exception class for retry
class RetryException(Exception):
    u_str = "Exception ({}) raised after {} tries."

    def __init__(self, exp, max_retry):
        self.exp = exp
        self.max_retry = max_retry    
    def __unicode__(self):
        return self.u_str.format(self.exp, self.max_retry)
    def __str__(self):
        return self.__unicode__()

# Define retry util function
def retry_func(func, max_retry=10):
    """
    @param func: The function that needs to be retry
    @param max_retry: Maximum retry of `func` function, default is `10`
    @return: func
    @raise: RetryException if retries exceeded than max_retry
    """
    for retry in range(1, max_retry + 1):
        try:
            return func()
        except Exception, e:
            logger.info('Failed to call {}, in retry({}/{})'.format(func.func,
                                                           retry, max_retry))
    else:
        raise RetryException(e, max_retry)

使用它：

from functools import partial
import requests

def some_request(uri, post):
    req = requests.post(uri, post)
    return req

uri = 'http://someuri.com'
post = {'test': 'yes'}

try:
    retry_func(partial(some_request, uri, post), max_retry=3)
except RetryException, e:
    print(e)

输出：

INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): someuri.com
INFO:retry:Failed to call <function some_request at 0x7faaba2318c0>, in retry(1/3)
INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): someuri.com
INFO:retry:Failed to call <function some_request at 0x7faaba2318c0>, in retry(2/3)
INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): someuri.com
INFO:retry:Failed to call <function some_request at 0x7faaba2318c0>, in retry(3/3)
Exception (HTTPConnectionPool(host='someuri.com', port=80): Max retries exceeded with url: / (Caused by <class 'socket.gaierror'>: [Errno -2] Name or service not known)) raised after 3 tries.

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