Python SOAP Client – use SUDS or something else?

While there isn’t a certified standard, if you must use SOAP, Suds is your best choice. Suds can be slow on large WSDLs, and that is something they are working on.

In the meantime, if you don’t expect your WSDL to change often, you have two options that can buy you a lot of speed:

1. Downloading your WSDL to localhost
2. Using caching

Downloading your WSDL

With large WSDLs part of the problem is that first you must download the WSDL every time, which can add overhead. Suds will take the time to download and parse the entire WSDL on startup to make sure that it hasn’t changed.

If you can download it to the local system and then pass it to the Client constructor using a file:// scheme in the URL. Since Suds uses urllib2 for the HTTP transport, this is perfectly legit.

Now, because you’re not providing a hostname in your WSDL URL, you will also have to pass a location argument specifying the actual URL of the SOAP application.

Here is an example:

from suds.client import Client

# The service URL
soap_url = 'http://myapp.example.notreal/path/to/soap'

# The WSDL URL, we wont' use this but just illustrating for example. This 
# would be the file you download to your system and save as wsdl_file
wsdl_url = 'http://myapp.example.notreal/path/to/soap?wsdl' 

# The full path to the downloaded WSDL file on your local system
wsdl_file = '/path/to/myapp.wsdl'
wsdl_url = 'file://' + wsdl_file # Override original wsdl_url

client = Client(url=wsdl_url, location=soap_url)

If you’re interested, I have used this approach in my work and have open sourced the code.

Caching your WSDL

The other option is to use Suds’ excellent caching feature. You must explicitly create a cache object and then pass that to the constructor using the cache argument. Otherwise it defaults to an ObjectCache with a duration of 1 day.

You might also consider using both of these approaches.