Diving In

Philosophically, I can describe HTTP web services in 12 words: exchanging data with remote servers using nothing but the operations of HTTP. If you want to get data from the server, use HTTP GET. If you want to send new data to the server, use HTTP POST. Some more advanced HTTP web service apis also allow creating, modifying, and deleting data, using HTTP PUT and HTTP DELETE. That’s it. No registries, no envelopes, no wrappers, no tunneling. The “verbs” built into the HTTP protocol (GET, POST, PUT, and DELETE) map directly to application-level operations for retrieving, creating, modifying, and deleting data.

The main advantage of this approach is simplicity, and its simplicity has proven popular. Data — usually XML or JSON — can be built and stored statically, or generated dynamically by a server-side script, and all major programming languages (including Python, of course!) include an HTTP library for downloading it. Debugging is also easier; because each resource in an HTTP web service has a unique address (in the form of a URL), you can load it in your web browser and immediately see the raw data.

Examples of HTTP web services:

Python 3 comes with two different libraries for interacting with HTTP web services:

  • http.client is a low-level library that implements RFC 2616, the HTTP protocol.
  • urllib.request is an abstraction layer built on top of http.client. It provides a standard API for accessing both HTTP and FTP servers, automatically follows http redirects, and handles some common forms of HTTP authentication.

So which one should you use? Neither of them. Instead, you should use httplib2, an open source third-party library that implements HTTP more fully than http.client but provides a better abstraction than urllib.request.

To understand why httplib2 is the right choice, you first need to understand HTTP.

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