I am trying to develop a small web application using python's WSGI. For example, if a user chooses Google they would be redirected to google.com, if they chose Facebook they'd be redirected to facebook.com, etc.
from wsgiref.simple_server import make_server
from cgi import parse_qs, escape
main_html = """
<html>
<head><title> Welcome to redirection test page </title> </head>
<body>
<form method="get" action='/visit'>
<input type=radio name='site' value=google> Google
<input type=radio name='site' value=facebook> Facebook
<input type=submit value=submit>
</form>
</body>
</html>
"""
def main(environ, start_response):
response_body = main_html
print type(response_body)
status = '200 OK'
response_headers = [
('Content-Type','text/html'),
('Content-Length', str(len(response_body)))
]
start_response(status, response_headers)
return [response_body]
def visit(environ, start_response):
qs = parse_qs(environ['QUERY_STRING'])
dest = qs.ge('site')[0]
if dest == 'google':
start_response('301 Moved Permanently', [('Location','http://google.com')])
else:
start_response('301 Moved Permanently', [('Location','http://facebook.com')])
return [1]
def app(environ, start_response):
if environ['PATH_INFO'] == '/':
return main(environ, start_response)
elif environ['PATH_INFO'] == '/visit':
return visit(environ, start_response)
httpd = make_server('192.168.48.128',8052, app)
print 'Serving on port 8052'
httpd.serve_forever()
However, when I run this code, I get the following error:
Traceback (most recent call last):
File "/usr/lib/python2.7/wsgiref/handlers.py", line 86, in run
self.finish_response()
File "/usr/lib/python2.7/wsgiref/handlers.py", line 131, in finish_response
self.close()
File "/usr/lib/python2.7/wsgiref/simple_server.py", line 33, in close
self.status.split(' ',1)[0], self.bytes_sent
AttributeError: 'NoneType' object has no attribute 'split'
You have two problems, both within visit(). The first is a typo, and the second is a failure to adhere to the WSGI specification
def visit(environ, start_response):
qs = parse_qs(environ['QUERY_STRING'])
dest = qs.ge('site')[0]
if dest == 'google':
start_response('301 Moved Permanently', [('Location','http://google.com')])
else:
start_response('301 Moved Permanently', [('Location','http://facebook.com')])
return [1]
Look at the line dest = qs.ge('site')[0]. qs is just a dictionary, and doesn't have a method ge, just get. Furthermore, cgi.parse_qs is deprecated - use urlparse.parse_qs() instead. Fixing that gets us a new error (my address is 127.0.0.1 because I just ran it off of localhost):
127.0.0.1 - - [05/Feb/2015 16:45:17] "GET /visit?site=facebook HTTP/1.1" 302 0
Traceback (most recent call last):
File "C:\Python27\lib\wsgiref\handlers.py", line 86, in run
self.finish_response()
File "C:\Python27\lib\wsgiref\handlers.py", line 128, in finish_response
self.write(data)
File "C:\Python27\lib\wsgiref\handlers.py", line 204, in write
assert type(data) is StringType, "write() argument must be string"
AssertionError: write() argument must be string
This tells us that something should be a string, but isn't. Looking again at visit(), at the return line, reveals the problem. You're returning [1] instead of ['1']. Fixing that error makes everything work fine. You'll find that this behavior is documented in PEP 333
The start_response callable must return a write(body_data) callable that takes one positional parameter: a string to be written as part of the HTTP response body.
Lastly, as per this answer, you should probably be using a '302 Found' status instead of '301 Moved Permanently' for a redirect, but it works either way.
Replacing the function with this should fix your issue:
def visit(environ, start_response):
qs = parse_qs(environ['QUERY_STRING'])
dest = qs.get('site')[0]
if dest == 'google':
start_response('302 Found', [('Location','http://google.com')])
else:
start_response('302 Found', [('Location','http://facebook.com')])
return ['1']