'Class' Attribute has no attribute 'variable'

Question

I am aware such issues have been raised quite often already. Still, after reviewing plenty of threads I was not able to identify the issue.

#!/usr/bin/env python
# Reflects the requests with dummy responses from HTTP methods GET, POST, PUT, and DELETE
# Written by Tushar Dwivedi (2017)


import json
# from BaseHTTPServer import HTTPServer, BaseHTTPRequestHandler
import sys
sys.path.append(r'C:\Users\[...]')
from http.server import BaseHTTPRequestHandler,HTTPServer
from optparse import OptionParser

class RequestHandler(BaseHTTPRequestHandler):

    def __init__(self, *args, **kwargs):
        BaseHTTPRequestHandler.__init__(self, *args, **kwargs)
        self.dummy_var = None

    def do_GET(self):
        request_path = self.path

        print("\n----- Request Start ----->\n")
        print("request_path :", request_path)
        print("self.headers :", self.headers)
        print("<----- Request End -----\n")

        self.send_response(200)
        self.send_header("Set-Cookie", "foo=bar")
        self.end_headers()

        self.wfile.write(json.dumps({'value_1': str(self.calc_value()), 'value_2': '0'}).encode())

    def calc_value(self):
        if self.dummy_var is None:
            self.dummy_var = 0

        self.dummy_var = self.dummy_var + 1

        return self.dummy_var

    do_PUT = do_POST
    do_DELETE = do_GET

def main():
    port = 8000
    print('Listening on localhost:%s' % port)
    server = HTTPServer(('', port), RequestHandler)
    server.serve_forever()

if __name__ == "__main__":
    parser = OptionParser()
    parser.usage = ("Creates an http-server that will echo out any GET or POST parameters, and respond with dummy data\n"
                    "Run:\n\n")
    (options, args) = parser.parse_args()

    main()

I am starting the server and making a request from a second script,

r = requests.get('http://localhost:8000').json()

Basic idea (for testing) is that each time the request is made, the dummy_var acts as a counter.

However, I get the following error:

  File "C:\Users\[...]\http_server.py", line 60, in calc_value
    if self.__dummy_var is None:
AttributeError: 'RequestHandler' object has no attribute 'dummy_var'

Any suggestions?

I did check the Indentation, but it seems to be all spaces, no tabs.

You can set attribute and then, use super() for inheritance: self.dummy_var = None super().__init__(*args, **kwargs) — Baris
– Baris, Commented Jun 12, 2020 at 17:08
Hi @Baris this indeed did resolve the AttributeError, so thanks a lot! Just another question: the counter (calc_value()) does not seem to work properly. Do you know if a class instance is created each time the request.get('...') in the second script is used? It seems for each request the init method of the RequestHandler Class is called.. — mulm
– mulm, Commented Jun 12, 2020 at 17:33
Hi @mulm, you're welcome. Unfortunately, I don't have an answer to this question. — Baris
– Baris, Commented Jun 12, 2020 at 17:43
You're pass the class , not an instance of it in the server = HTTPServer(('', port), RequestHandler) statement. — martineau
– martineau, Commented Jun 12, 2020 at 17:44

Baris · Accepted Answer · 2020-06-12 17:52:27Z

1

Since it's difficult to see the necessary changes from comments, I think it's worth sharing it here.

The solution is setting the attribute before calling __init__(), and using super() for cooperative inheritance. So, init method should be changed with the following lines:

def __init__(self, *args, **kwargs):
    self.dummy_var = None 
    super().__init__(*args, **kwargs)

answered Jun 12, 2020 at 17:52

Baris

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