Logon to Web Site and Download File Programmatically using Python, urllib2 module

DoveTails
DoveTails used Ask the Experts™
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Wish to logon to web site to programmatically download data.
Looking for assistance with Python and the urllib2 module.

At this page:
  https://www.nifc.blm.gov/cgi/WfmiHome.cgi
there is a Logon button which uses a GET (not a Post) referring to:
    https://www.nifc.blm.gov/cgi/WfmiHome.cgi/Page/Logon
which Redirects to: https://www.nifc.blm.gov/cgi/WfmiHome.cgi/Page/DoiMonitor

I'm hoping to understand how to navigate through web pages to eventually logon with my account.  
I've tried many variations of the below code without success.
Need help understand urllib2 to navigate to page with "I Agree" button and then to the actual page to enter username and password.
mport urllib
import urllib2
import cookielib

#cookie storage
cj = cookielib.CookieJar()
opener = urllib2.build_opener(
    urllib2.HTTPCookieProcessor(cj),
    urllib2.HTTPRedirectHandler
    )

#### First page
url = 'https://www.nifc.blm.gov/cgi/WfmiHome.cgi'

request = urllib2.Request(url)

response = urllib2.urlopen(request)

html = response.read()

# Print to screen
print html 

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Appreciate help ...  Thanks !
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Walter RitzelSenior Software Engineer

Commented:
You would need 2 things:
1) create a code similar to yours to submit the information for the logon page;
2) make sure that a session is being maintained;
3) call the download url, using the code you have showed.

It is not a question of navigating through pages, but a matter of generate the session that you need with the logon page and then call the direct download url.
Thanks for the response Walter.
My thinking behind navigating through the first few pages with buttons specifying "Logon" and "I Agree" is to acquire the necessary cookies.  If I attempt to navigate directly to the Authentication Page, I am directed back to the main Home page with the "Logon" button (basically back to page 1).

I'm assuming by pressing "I Agree" in a standard browser a cookie is set which lasts for that session.

Hopefully the code I have worked on for a Post with the logon information will work, but I cannot programmatically get to the logon page and my guess for that is because I do not yet have the "I Agree" cookie.

Any thoughts ?
Senior Software Engineer
Commented:
In this case, instead of using urllib2, you may be interested on using mechanize.

http://www.pythonforbeginners.com/mechanize/browsing-in-python-with-mechanize/

It uses urllib under the covers, but maybe the piece of functionality you are looking for is already implemented there.
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Another library, that I can strongly recommend for any access to web servers, that are NOT using javascript is
requests:

https://pypi.python.org/pypi/requests


For any web page containing loads of javascript it might be necesseray to use a real web browser and to automate it.

you could use Selenium, which allows you to automate a browser
https://pypi.python.org/pypi/selenium

Please reply if you're interested in either requests or selenium.


I personally gave up on using urllib in my code. I think its only advantage is, that it is a standard python module, but coding with it just looks clumsy to me.
nociSoftware Engineer
Distinguished Expert 2018
Commented:
maybe, probably, you are accomplishing the same thing as what curl (curllib) already does.
Check http://curl.haxx.se for more info on curl.

It has support for http, https, telnet, ftp, ftps,  etc. etc. and using the command line interface you can script  access to webservers including logins etc. excluding JS execution. (no ajax...). It can handle cookies that way too. the library version is more flexible. still no ajax though.... unless you have JS interpreter built into your software.
Thank you.  More options than I expected.
Appreciate your input !

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