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How to send cookies with urllib

I'm attempting to connect to a website that requires you to have a specific cookie to access it. For the sake of this question, we'll call the cookie 'required_cookie' and the value 'required_value'.
This is my code:
import urllib
import http.cookiejar
cj = http.cookiejar.CookieJar()
opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
opener.addheaders = [('required_cookie', 'required_value'), ('User-Agent', 'Mozilla/5.0')]
urllib.request.install_opener(opener)
req = Request('https://www.thewebsite.com/')
webpage = urlopen(req).read()
print(webpage)
I'm new to urllib so please answer me as a beginner

To do this with urllib, you need to:
Construct a Cookie object. The constructor isn't documented in the docs, but if you help(http.cookiejar.Cookie) in the interactive interpreter, you can see that its constructor demands values for all 16 attributes. Notice that the docs say, "It is not expected that users of http.cookiejar construct their own Cookie instances."
Add it to the cookiejar with cj.set_cookie(cookie).
Tell the cookiejar to add the correct headers to the request with cj.add_cookie_headers(req).
Assuming you've configured the policy correctly, you're set.
But this is a huge pain. As the docs for urllib.request say:
See also The Requests package is recommended for a higher-level HTTP client interface.
And, unless you have some good reason you can't install requests, you really should go that way. urllib is tolerable for really simple cases, and it can be handy when you need to get deep under the covers—but for everything else, requests is much better.
With requests, your whole program becomes a one-liner:
webpage = requests.get('https://www.thewebsite.com/', cookies={'required_cookie': required_value}, headers={'User-Agent': 'Mozilla/5.0'}).text
… although it's probably more readable as a few lines:
cookies = {'required_cookie': required_value}
headers = {'User-Agent': 'Mozilla/5.0'}
response = requests.get('https://www.thewebsite.com/', cookies=cookies, headers=headers)
webpage = response.text

With the help of Kite documentation: https://www.kite.com/python/answers/how-to-add-a-cookie-to-an-http-request-using-urllib-in-python
You can add cookie this way:
import urllib
a_request = urllib.request.Request("http://www.kite.com/")
a_request.add_header("Cookie", "cookiename=cookievalue")
or in a different way:
from urllib.request import Request
url = "https://www.kite.com/"
req = Request(url, headers={'User-Agent': 'Mozilla/5.0', 'Cookie':'myCookie=lovely'})

Python requests lib, is requests.Session equivalent to urllib2's opener?

I need to accomplish a login task in my own project.Luckily I found someone has it done already.
Here is the related code.
import re,urllib,urllib2,cookielib
class Login():
cj = cookielib.LWPCookieJar()
opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj))
def __init__(self,name='',password='',domain=''):
self.name=name
self.password=password
self.domain=domain
urllib2.install_opener(self.opener)
def login(self):
params = {'domain':self.domain,'email':self.name,'password':self.password}
req = urllib2.Request(
website_url,
urllib.urlencode(params)
)
self.openrate = self.opener.open(req)
print self.openrate.geturl()
info = self.openrate.read()
I've tested the code, it works great (according to info).
Now I want to port it to Python 3 as well as using requests lib instead of urllib2.
My thoughts:
since the original code use opener, though not sure, I think its equivalent in requests is requests.Session
Am I supposed to pass in a jar = cookiejar.CookieJar() when making request? Not sure either.
I've tried something like
import requests
from http import cookiejar
from urllib.parse import urlencode
jar = cookiejar.CookieJar()
s = requests.Session()
s.post(
website_url,
data = urlencode(params),
allow_redirects = True,
cookies = jar
)
Also, followed the answer in Putting a `Cookie` in a `CookieJar`, I tried making the same request again, but none of these worked.
That's why I'm here for help.
Will someone show me the right way to do this job? Thank you~

An opener and a Session are not entirely analogous, but for your particular use-case they match perfectly.
You do not need to pass a CookieJar when using a Session: Requests will automatically create one, attach it to the Session, and then persist the cookies to the Session for you.
You don't need to urlencode the data: requests will do that for you.
allow_redirects is True by default, you don't need to pass that parameter.
Putting all of that together, your code should look like this:
import requests
s = requests.Session()
s.post(website_url, data = params)
Any future requests made using the Session you just created will automatically have cookies applied to them if they are appropriate.

Establishing session with web app to crawl

I am planning to write a website crawler in Python using Requests and PyQuery.
However, the site I am targeting requires me to be signed into my account. Using Requests, is it possible for me to establish a session with the server (using my credentials for the site), and use this session to crawl sites that I have access to only when logged in?
I hope this question is clear, thank you.

Yes it is possible.
I don't know about PyQuery but I've made crawlers that log in to sites using urllib2.
All you need is to use cookiejar to handle cookies and send the login form using a request.
If you ask something more specific I will try to be more explicit too.
LE:
urllib2 is not a mess. It's the best library for such things in my opinion.
Here's a code snipet that will log in to a site (after that you can just parse the site normally):
import urllib
import urllib2
import cookielib
"""Adding cookie support"""
cj = cookielib.CookieJar()
opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj))
urllib2.install_opener(opener)
"""Next we will log in to the site. The actual url will be different and also the data.
You should check the log in form to see what parameters it takes and what values.
"""
data = {'username' : 'foo',
'password' : 'bar'
}
data = urllib.urlencode(data)
urllib2.urlopen('http://www.siteyouwanttoparse.com/login', data) #this should log us in
"""Now you can parse the site"""
html = urllib2.urlopen('http://www.siteyoutwanttoparse.com').read()
print html

session error ? using POST using requests or urllib2

trying to authenticate to a website and fill out a form using requests lib
import requests
payload = {"name":"someone", "password":"somepass", "submit":"Submit"}
s = requests.Session()
s.post("https://someurl.com", data=payload)
next_payload = {"item1":"something", "item2":"something", "submit":"Submit"}
r = s.post("https://someurl.com", data=next_payload)
print r.text
authentication works and i verified that i can post to forms but this one i am having problem with gives The action could not be completed, perhaps because your session had expired. Please try again
Attempted in urllib2 and same result -- dont think its an issue with a cookie.
I am wondering if javascript on this page has something to do with giving session error? other form page doesnt have any javascripts.
Thanks for your input...

Using urllib2 via proxy

I am trying to use urllib2 through a proxy; however, after trying just about every variation of passing my verification details using urllib2, I either get a request that hangs forever and returns nothing or I get 407 Errors. I can connect to the web fine using my browser which connects to a prox-pac and redirects accordingly; however, I can't seem to do anything via the command line curl, wget, urllib2 etc. even if I use the proxies that the prox-pac redirects to. I tried setting my proxy to all of the proxies from the pac-file using urllib2, none of which work.
My current script looks like this:
import urllib2 as url
proxy = url.ProxyHandler({'http': 'username:password#my.proxy:8080'})
auth = url.HTTPBasicAuthHandler()
opener = url.build_opener(proxy, auth, url.HTTPHandler)
url.install_opener(opener)
url.urlopen("http://www.google.com/")
which throws HTTP Error 407: Proxy Authentication Required and I also tried:
import urllib2 as url
handlePass = url.HTTPPasswordMgrWithDefaultRealm()
handlePass.add_password(None, "http://my.proxy:8080", "username", "password")
auth_handler = url.HTTPBasicAuthHandler(handlePass)
opener = url.build_opener(auth_handler)
url.install_opener(opener)
url.urlopen("http://www.google.com")
which hangs like curl or wget timing out.
What do I need to do to diagnose the problem? How is it possible that I can connect via my browser but not from the command line on the same computer using what would appear to be the same proxy and credentials?
Might it be something to do with the router? if so, how can it distinguish between browser HTTP requests and command line HTTP requests?

Frustrations like this are what drove me to use Requests. If you're doing significant amounts of work with urllib2, you really ought to check it out. For example, to do what you wish to do using Requests, you could write:
import requests
from requests.auth import HTTPProxyAuth
proxy = {'http': 'http://my.proxy:8080'}
auth = HTTPProxyAuth('username', 'password')
r = requests.get('http://wwww.google.com/', proxies=proxy, auth=auth)
print r.text
Or you could wrap it in a Session object and every request will automatically use the proxy information (plus it will store & handle cookies automatically!):
s = requests.Session(proxies=proxy, auth=auth)
r = s.get('http://www.google.com/')
print r.text