Question

我正在尝试确定为什么我正在返回的Response对象在运行多次时被相同的脚本处理不同？当脚本成功时，响应对象以<class 'requests.models.Response'>传递，当它失败时，它会丢失所有属性并以<type 'NoneType'>传递，我不知道如何？

其他详情：

我正在运行一个脚本，使用Python 2.7和请求通过API登录并注销Tableau Server。该脚本正在通过SSH连接运行到我们的数据库，我得到了一些奇怪的结果。

如果在第一次尝试发布请求时没有成功，它将失败但在我到达该点之前需要从2次尝试到7次尝试。

剧本：

import time
import requests
import sys
import xml.etree.ElementTree as ET


class TableauHook():

    def __init__(self):
        self.url = 'https://{server}.com/api/2.8/'
        self.username = 'username'
        self.password = 'password'
        self.name = 'datasource_name'
        self.auth_header = None
        self.sign_in = self._sign_in()


    def _sign_in(self):
        endpoint = 'auth/signin'
        payload = '<tsRequest><credentials name="{name}" password="{pw}" ><site contentUrl="" /></credentials></tsRequest>'.format(
            name=self.username, pw=self.password)
        # Request setup
        req = self.send_request(req_type='post', endpoint=endpoint, payload=payload)
        print('Returned req: ' + str(type(req)))


        if req.content:
            print('Sign in to Tableau: Success')
            response = ET.fromstring(req.content)

            # Parse and store request data
            self.token = response.find('.//t:credentials',
                                       namespaces={'t': "http://tableau.com/api"}).attrib['token']
            self.site_id = response.find('.//t:site',
                                         namespaces={'t': "http://tableau.com/api"}).attrib['id']
            self.auth_header = {'X-tableau-auth': self.token}

            print('Token: exists' )
            print('Site id: exists')
            print('Auth_header: exists' )
        else:
            print('Sign in to Tableau unsuccessful')


    def send_request(self, req_type, endpoint, payload=None, attempts=None):
        # Count attempts to send request
        if attempts == None:
            attempts = 1
        else:
            attempts = attempts

        if attempts > 20:
            sys.exit('Too many attempts made')

        print('\nAttempt: ' + str(attempts))
        print('Endpoint: ' + endpoint)
        # Send request/load response
        try:
            if req_type.upper() == 'POST':
                response = requests.post(self.url + endpoint, data=payload, headers=self.auth_header)
                print('Response: ' + str(type(response)))
                if type(response) == type(None):
                    print('Response is NoneType')
                    raise Exception('NoneType returned')
                return response
            elif req_type.upper() == 'GET':
                response = requests.get(self.url + endpoint, data=payload, headers=self.auth_header)
                print('Response: ' + str(type(response)))
                if type(response) == type(None):
                    raise Exception('NoneType returned')
                return response

        except Exception as e:
            print('Error: ' + str(e))
            print('Sleeping for 3 seconds...')
            time.sleep(3)
            attempts += 1
            print('Running send_request() again')
        self.send_request(req_type=req_type, endpoint=endpoint, payload=payload, attempts=attempts)



    def sign_out(self):
        endpoint = 'auth/signout'
        try:
            req = requests.post(self.url+endpoint, headers=self.auth_header)
        except Exception as e:
            print(e)
            time.sleep(3)
            req = requests.post(self.url + endpoint, headers=self.auth_header)
        print('Returned response: ' + str(type(req)))
        print(req)
        print('\n')

def main():
    hook = TableauHook()
    print('\nSigning out\n')
    hook.sign_out()


if __name__ == '__main__':
    main()

以下是两次尝试的控制台输出：

# First attempt to run the script
[user@databox directory]$ python TableauDBTest.py 

Attempt: 1
Endpoint: auth/signin
Response: <class 'requests.models.Response'>
Returned req: <class 'requests.models.Response'>
Sign in to Tableau: Success
Token: exists
Site id: exists
Auth_header: exists

Signing out

Returned response: <class 'requests.models.Response'>
<Response [204]>

# Run the script again, this time with different results
[user@databox directory]$ python TableauDBTest.py 

Attempt: 1
Endpoint: auth/signin
Error: ('Connection aborted.', error(104, 'Connection reset by peer'))
Sleeping for 3 seconds...
Running send_request() again

Attempt: 2
Endpoint: auth/signin
Response: <class 'requests.models.Response'>
Returned req: <type 'NoneType'>
Traceback (most recent call last):
  File "TableauDBTest.py", line 115, in <module>
    main()
  File "TableauDBTest.py", line 109, in main
    hook = TableauHook()
  File "TableauDBTest.py", line 15, in __init__
    self.sign_in = self._sign_in()
  File "TableauDBTest.py", line 27, in _sign_in
    if req.content:
AttributeError: 'NoneType' object has no attribute 'content'

提前感谢您对可能导致此问题的任何想法！

Answer 1

您的send_request方法以递归方式调用self.send_request，但它没有返回值;它只是忽略它然后从函数的末尾掉下来并返回None。

因此，最简单的解决方法是更改最后一行：

self.send_request(req_type=req_type, endpoint=endpoint, payload=payload, attempts=attempts)

......对此：

return self.send_request(req_type=req_type, endpoint=endpoint, payload=payload, attempts=attempts)

但是，将它重写为循环而不是使用递归会更简单：

def send_request(self, req_type, endpoint, payload=None):
    for attempt in range(1, 21):
        print(etc.)
        try:
            stuff
            return response
        except blah blah:
            ...
    sys.exit('Too many attempts made')

Python：什么可能导致请求对象丢失属性？

1 个答案: