web.redirect() not working in web.py

Question

I am working on a project using web.py framework. I have a small code for redirecting a user to a different screen if the result returned from a database query is blank (or number of rows returned is zero).

voma_user_details = get_user_by_email(['id','is_active'],None,email)
if len(list(voma_user_details)) == 0:
    #return redirect_url+'?error=User not found in database'
    web.redirect(redirect_url+'?error=User not found in database')      
voma_id = int(voma_user_details[0]['id'])

Here when the query returns zero records, the page should be redirected to redirect_url, however the redirect does not work and it raises an exception on the next line i.e. list index out of range (as the list length is zero). I checked by printing the redirect url in the if block, it goes into the block but does not redirect the page.

Any pointers will be highly appreciated.

mata · Accepted Answer · 2013-06-27 15:57:47Z

2

web.redirect returns a Redirect object, which is an instance of Exception.

You should raise it (or you may also return it) to cause the redirection to happen.

Otherwise the rest of the method will still be executed, which may cause an unrelated exception (in this case an an IndexError because you're trying to get an element of an empty list).

If you only call web.redirect the returned string will be sent as response content, but the response header will still contain the redirection (using status 301). But browsers usually follow 301 redirections immediately.

edited Jun 27, 2013 at 15:57

answered Jun 27, 2013 at 11:55

mata

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2 Comments

Ankit Jaiswal Over a year ago

The same code was working previously. It broke when I added some more redirects to the script. However I will try using it with return or raise.

mata Over a year ago

@AnkitJaiswal - ok, I was wrong, simply calling redirect does set the 301 status and add the location hresponse header. I've updated my answer.

Zhang Huangbin · Accepted Answer · 2013-06-27 14:18:55Z

1

Looks like web.seeother() is what you want: http://webpy.org/cookbook/redirect%20seeother

I use "raise web.seeother(xx)" a lot, but no web.redirect() yet. Quote from above link:

It's unlikely that you want to use the web.redirect function very often -- it appears to do the same thing, but it sends the http code 301, which is a permanent redirect. Most web browsers will cache the new redirection, and will send you to that location automatically when you try to perform the action again. A good use case for redirect is when you're changing the URL structure of your site, but want the old links to work due to bookmarking.

answered Jun 27, 2013 at 14:18

Zhang Huangbin

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1 Comment

Ankit Jaiswal Over a year ago

I used web.seeother() first but was facing the same issue with it also. Then I tried web.redirect() and it worked earlier. It stopped when I added some more redirect conditions.

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