What are the differences between the urllib, urllib2, urllib3 and requests module?

I know it's been said already, but I'd highly recommend the requests Python package.

If you've used languages other than python, you're probably thinking urllib and urllib2 are easy to use, not much code, and highly capable, that's how I used to think. But the requests package is so unbelievably useful and short that everyone should be using it.

First, it supports a fully restful API, and is as easy as:

import requestsresp = requests.get('http://www.mywebsite.com/user')resp = requests.post('http://www.mywebsite.com/user')resp = requests.put('http://www.mywebsite.com/user/put')resp = requests.delete('http://www.mywebsite.com/user/delete')

Regardless of whether GET / POST, you never have to encode parameters again, it simply takes a dictionary as an argument and is good to go:

userdata = {"firstname": "John", "lastname": "Doe", "password": "jdoe123"}resp = requests.post('http://www.mywebsite.com/user', data=userdata)

Plus it even has a built in JSON decoder (again, I know json.loads() isn't a lot more to write, but this sure is convenient):

resp.json()

Or if your response data is just text, use:

resp.text

This is just the tip of the iceberg. This is the list of features from the requests site:

• International Domains and URLs
• Keep-Alive & Connection Pooling
• Sessions with Cookie Persistence
• Browser-style SSL Verification
• Basic/Digest Authentication
• Elegant Key/Value Cookies
• Automatic Decompression
• Unicode Response Bodies
• Multipart File Uploads
• Connection Timeouts
• .netrc support
• List item
• Python 2.7, 3.6—3.9
• Thread-safe.

urllib2 provides some extra functionality, namely the urlopen() function can allow you to specify headers (normally you'd have had to use httplib in the past, which is far more verbose.) More importantly though, urllib2 provides the Request class, which allows for a more declarative approach to doing a request:

r = Request(url='http://www.mysite.com')r.add_header('User-Agent', 'awesome fetcher')r.add_data(urllib.urlencode({'foo': 'bar'})response = urlopen(r)

Note that urlencode() is only in urllib, not urllib2.

There are also handlers for implementing more advanced URL support in urllib2. The short answer is, unless you're working with legacy code, you probably want to use the URL opener from urllib2, but you still need to import into urllib for some of the utility functions.

Bonus answerWith Google App Engine, you can use any of httplib, urllib or urllib2, but all of them are just wrappers for Google's URL Fetch API. That is, you are still subject to the same limitations such as ports, protocols, and the length of the response allowed. You can use the core of the libraries as you would expect for retrieving HTTP URLs, though.

This is my understanding of what the relations are between the various "urllibs":

In the Python 2 standard library there exist two HTTP libraries side-by-side. Despite the similar name, they are unrelated: they have a different design and a different implementation.

• urllib was the original Python HTTP client, added to the standard library in Python 1.2. Earlier documentation for urllib can be found in Python 1.4.

• urllib2 was a more capable HTTP client, added in Python 1.6, intended as a replacement for urllib:

  urllib2 - new and improved but incompatible version of urllib (still experimental).

  Earlier documentation for urllib2 can be found in Python 2.1.

The Python 3 standard library has a new urllib which is a merged/refactored/rewritten version of the older modules.

urllib3 is a third-party package (i.e., not in CPython's standard library). Despite the name, it is unrelated to the standard library packages, and there is no intention to include it in the standard library in the future.

Finally, requests internally uses urllib3, but it aims for an easier-to-use API.