urllib3 Documentation

Highlights

  • Re-use the same socket connection for multiple requests, with optional client-side certificate verification. See: HTTPConnectionPool and HTTPSConnectionPool
  • File posting. See: encode_multipart_formdata()
  • Built-in redirection and retries (optional).
  • Supports gzip and deflate decoding. See: decode_gzip() and decode_deflate()
  • Thread-safe and sanity-safe.
  • Tested on Python 2.6+ and Python 3.2+, 100% unit test coverage.
  • Works with AppEngine, gevent, and eventlib.
  • Small and easy to understand codebase perfect for extending and building upon. For a more comprehensive solution, have a look at Requests which is also powered by urllib3.

Getting Started

Installing

pip install urllib3 or fetch the latest source from github.com/shazow/urllib3.

Usage

>>> import urllib3
>>> http = urllib3.PoolManager()
>>> r = http.request('GET', 'http://google.com/')
>>> r.status
200
>>> r.headers['server']
'gws'
>>> r.data
...

Components

urllib3 tries to strike a fine balance between power, extendability, and sanity. To achieve this, the codebase is a collection of small reusable utilities and abstractions composed together in a few helpful layers.

PoolManager

The highest level is the PoolManager(...).

The PoolManager will take care of reusing connections for you whenever you request the same host. This should cover most scenarios without significant loss of efficiency, but you can always drop down to a lower level component for more granular control.

>>> http = urllib3.PoolManager(10)
>>> r1 = http.request('GET', 'http://google.com/')
>>> r2 = http.request('GET', 'http://google.com/mail')
>>> r3 = http.request('GET', 'http://yahoo.com/')
>>> len(http.pools)
2

A PoolManager is a proxy for a collection of ConnectionPool objects. They both inherit from RequestMethods to make sure that their API is similar, so that instances of either can be passed around interchangeably.

ProxyManager

The ProxyManager is an HTTP proxy-aware subclass of PoolManager. It produces a single HTTPConnectionPool instance for all HTTP connections and individual per-server:port HTTPSConnectionPool instances for tunnelled HTTPS connections:

>>> proxy = urllib3.ProxyManager('http://localhost:3128/')
>>> r1 = proxy.request('GET', 'http://google.com/')
>>> r2 = proxy.request('GET', 'http://httpbin.org/')
>>> len(proxy.pools)
1
>>> r3 = proxy.request('GET', 'https://httpbin.org/')
>>> r4 = proxy.request('GET', 'https://twitter.com/')
>>> len(proxy.pools)
3

ConnectionPool

The next layer is the ConnectionPool(...).

The HTTPConnectionPool and HTTPSConnectionPool classes allow you to define a pool of connections to a single host and make requests against this pool with automatic connection reusing and thread safety.

When the ssl module is available, then HTTPSConnectionPool objects can be configured to check SSL certificates against specific provided certificate authorities.

>>> conn = urllib3.connection_from_url('http://www.google.com')
>>> r1 = conn.request('GET', 'http://www.google.com/')
>>> r2 = conn.request('GET', '/search')
>>> r3 = conn.request('GET', 'http://wwww.yahoo.com/')
Traceback (most recent call last)
  ...
HostChangedError: Connection pool with host 'http://google.com' tried to
open a foreign host: http://yahoo.com/

Again, a ConnectionPool is a pool of connections to a specific host. Trying to access a different host through the same pool will raise a HostChangedError exception unless you specify assert_same_host=False. Do this at your own risk as the outcome is completely dependent on the behaviour of the host server.

If you need to access multiple hosts and don’t want to manage your own collection of ConnectionPool objects, then you should use a PoolManager.

A ConnectionPool is composed of a collection of httplib.HTTPConnection objects.

Timeout

A timeout can be set to abort socket operations on individual connections after the specified duration. The timeout can be defined as a float or an instance of Timeout which gives more granular configuration over how much time is allowed for different stages of the request. This can be set for the entire pool or per-request.

::
>>> from urllib3 import PoolManager, Timeout
>>> # Manager with 3 seconds combined timeout.
>>> http = PoolManager(timeout=3.0)
>>> r = http.request('GET', 'http://httpbin.org/delay/1')
>>> # Manager with 2 second timeout for the read phase, no limit for the rest.
>>> http = PoolManager(timeout=Timeout(read=2.0))
>>> r = http.request('GET', 'http://httpbin.org/delay/1')
>>> # Manager with no timeout but a request with a timeout of 1 seconds for
>>> # the connect phase and 2 seconds for the read phase.
>>> http = PoolManager()
>>> r = http.request('GET', 'http://httpbin.org/delay/1', timeout=Timeout(connect=1.0, read=2.0))
>>> # Same Manager but request with a 5 second total timeout.
>>> r = http.request('GET', 'http://httpbin.org/delay/1', timeout=Timeout(total=5.0))

Foundation

At the very core, just like its predecessors, urllib3 is built on top of httplib – the lowest level HTTP library included in the Python standard library.

To aid the limited functionality of the httplib module, urllib3 provides various helper methods which are used with the higher level components but can also be used independently.

Contrib Modules

These modules implement various extra features, that may not be ready for prime time.

Notes

  • SSL/TLS compression is disabled by default on Python 3.2+ to migitate the CRIME attack. You can disable compression on Python 2 by using the pyopenssl contrib module, although this requires additional dependencies and might have undesired side effects due to the nature of PyOpenSSL.

Contributing

  1. Check for open issues or open a fresh issue to start a discussion around a feature idea or a bug. There is a Contributor Friendly tag for issues that should be ideal for people who are not very familiar with the codebase yet.
  2. Fork the urllib3 repository on Github to start making your changes.
  3. Write a test which shows that the bug was fixed or that the feature works as expected.
  4. Send a pull request and bug the maintainer until it gets merged and published. :) Make sure to add yourself to CONTRIBUTORS.txt.