urllib2 content-type headers

Philip Semanchuk philip at semanchuk.com
Sun Jun 21 19:08:46 CEST 2009

On Jun 21, 2009, at 12:01 PM, TYR wrote:

> I have a little application that wants to send data to a Google API.
> This API requires an HTTP header to be set as follows:
> Authorization: GoogleLogin auth=[value of auth token goes here]
> Unfortunately, I'm getting nothing but 400 Bad Requests. I suspect
> this is due to an unfeature of urllib2. Notably, although you can use
> urllib2.Request's add_header method to append a header, the
> documentation (http://docs.python.org/library/urllib2.html) says that:
> remember that a few standard headers (Content-Length, Content-Type and
> Host) are added when the Request is passed to urlopen() (or
> OpenerDirector.open()).
> And:
> Note that there cannot be more than one header with the same name, and
> later calls will overwrite previous calls in case the key collides.
> To put it another way, you cannot rely on Content-Type being correct
> because whatever you set it to explicitly, urllib2 will silently
> change it to something else which may be wrong, and there is no way to
> stop it. What happened to "explicit is better than implicit"?


I'm confused, are you having a problem with the Content-Type or  
Authorization headers?

Some suggestions --
- Try sending the request to a server you control so you can see what  
it is actually receiving. Maybe urllib2 isn't overwriting your header  
at all, but you're sending (e.g.) a misconfigured auth token.

- Use a protocol sniffer like Wireshark to see what's going out over  
the wire

- Urrlib2 automates some things for you (like building headers), but  
as with all automated magic sometimes it's not what you want. The  
httplib module offers finer control over HTTP conversations. You might  
want to use httplib to debug this problem even if you find you don't  
need it in your final solution.

good luck

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