Jorge Jorge - 1 month ago 9
Python Question

self.response.out.write() - how to use it properly?

I have a class that doesn't extend

webapp.RequestHandler
, and I can't use
self.response.out.write()
, I get:


AttributeError: Fetcher instance has no attribute 'response'


If I extend
webapp.RequestHandler
(I thought it would work), I get:


AttributeError: 'Fetcher' object has no attribute 'response'


How can I use that method properly? Sometimes
print
doesn't work either; I just get a blank screen.

EDIT:

app.yaml:

application: fbapp-lotsofquotes
version: 1
runtime: python
api_version: 1

handlers:
- url: .*
script: main.py


source (the problematic line is marked with
#<- HERE
):

import random
import os

from google.appengine.api import users, memcache
from google.appengine.ext import webapp, db
from google.appengine.ext.webapp import util, template
from google.appengine.ext.webapp.util import run_wsgi_app

import facebook


class Quote(db.Model):
author = db.StringProperty()
string = db.StringProperty()
categories = db.StringListProperty()
#rating = db.RatingProperty()


class Fetcher(webapp.RequestHandler):
'''
Memcache keys: all_quotes
'''

def is_cached(self, key):
self.fetched = memcache.get(key)
if self.fetched:
print 'ok'#return True
else:
print 'not ok'#return False


#TODO: Use filters!
def fetch_quotes(self):
quotes = memcache.get('all_quotes')
if not quotes:
#Fetch and cache it, since it's not in the memcache.
quotes = Quote.all()
memcache.set('all_quotes',quotes,3600)
return quotes

def fetch_quote_by_id(self, id):
self.response.out.write(id) #<---------- HERE


class MainHandler(webapp.RequestHandler):

def get(self):
quotes = Fetcher().fetch_quotes()
template_data = {'quotes':quotes}
template_path = 'many.html'
self.response.out.write(template.render(template_path, template_data))


class ViewQuoteHandler(webapp.RequestHandler):

def get(self, obj):
self.response.out.write('viewing quote<br/>\n')
if obj == 'all':
quotes = Fetcher().fetch_quotes()
self.render('view_many.html',quotes=quotes)
else:
quotes = Fetcher().fetch_quote_by_id(obj)
'''for quote in quotes:
print quote.author
print quote.'''


def render(self, type, **kwargs):
if type == 'single':
template_values = {'quote':kwargs['quote']}
template_path = 'single_quote.html'
elif type == 'many':
print 'many'

self.response.out.write(template.render(template_path, template_values))


'''
CREATORS
'''
class NewQuoteHandler(webapp.RequestHandler):

def get(self, action):
if action == 'compose':
self.composer()
elif action == 'do':
print 'hi'

def composer(self):
template_path = 'quote_composer.html'
template_values = ''
self.response.out.write(template.render(template_path,template_values))

def post(self, action):
author = self.request.get('quote_author')
string = self.request.get('quote_string')
print author, string

if not author or not string:
print 'REDIRECT'

quote = Quote()
quote.author = author
quote.string = string
quote.categories = []
quote.put()


def main():
application = webapp.WSGIApplication([('/', MainHandler),
(r'/view/quote/(.*)',ViewQuoteHandler),
(r'/new/quote/(.*)',NewQuoteHandler) ],
debug=True)
util.run_wsgi_app(application)


if __name__ == '__main__':
main()

Answer

You're not routing to Fetcher when you initialize a WSGIApplication. Rather, you create an instance manually in other handlers. Thus, App Engine will not initialize your request and response properties. You can manually do so in from the handlers you route to, such as MainHandler and ViewQuoteHandler. E.g.:

fetcher = Fetcher()
fetcher.initialize(self.request, self.response)
quotes = fetcher.fetch_quotes()

Note that fetcher really doesn't have to be a RequestHandler. It could be a separate class or function. Once you have request and response objects, you can pass them around as you choose.

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