how do I tell what extras are available?

[glyph]

I know I can pip install requests[security], but how do I know it's called "security" (other than reading the docs) and how do I know there aren't other things I also want to install? Can pip do this for me? Is there a tool outside of pip I should be using?

[rbtcollins]

Today the only way to know is to examine the metadata. This is static for wheels, and dynamic for everything else. I think it could be reasonable for pip to have a query mode to answer questions like this.

[dholth]

pkg_resources has an easy way to get at this information. Shown is how you would look at metadata for ipython on sys.path, but it is also possible to load metadata from any directory e.g. an uninstalled package:

>>> import pkg_resources
>>> pkg_resources.working_set.by_key['ipython'].extras
['all', 'doc', 'notebook', 'nbconvert', 'qtconsole', 'test', 'zmq', 'parallel']

>>> pkg_resources.working_set.by_key['ipython']._dep_map
{None: [],
 'all': [Requirement.parse('pyzmq>=2.1.11'),
  Requirement.parse('nose>=0.10.1'),
  Requirement.parse('tornado>=3.1'),
  Requirement.parse('Sphinx>=1.1'),
  Requirement.parse('pygments'),
  Requirement.parse('numpydoc'),
  Requirement.parse('Sphinx>=0.3'),
  Requirement.parse('jinja2')],
 'doc': [Requirement.parse('numpydoc'), Requirement.parse('Sphinx>=1.1')],
 'nbconvert': [Requirement.parse('jinja2'),
  Requirement.parse('pygments'),
  Requirement.parse('Sphinx>=0.3')],
 'notebook': [Requirement.parse('jinja2'),
  Requirement.parse('pyzmq>=2.1.11'),
  Requirement.parse('tornado>=3.1')],
 'parallel': [Requirement.parse('pyzmq>=2.1.11')],
 'qtconsole': [Requirement.parse('pyzmq>=2.1.11'),
  Requirement.parse('pygments')],
 'test': [Requirement.parse('nose>=0.10.1'), Requirement.parse('mock')],
 'zmq': [Requirement.parse('pyzmq>=2.1.11')]}

In wheels, there is a *.dist-info directory with METADATA. It has one Provides-Extra: line for each extra:

Provides-Extra: docs
Provides-Extra: testing

In *.egg-info, there is a requires.txt. This package has a [test] extra.

setuptools
pytz

[test]
python-dateutil

[glyph]

@dholth - there are not enough scare quotes in the world to put around “easy” in that first sentence :)

[rbtcollins]

@dholth I was assuming the request was for uninstalled packages :)

[dstufft]

Closing this, use pypi/warehouse#1855 instead.

[rbtcollins]

What about packages that aren't on warehouse? e.g. direct url references etc...

[dstufft]

@rbtcollins I'm not sure what you'd want pip to do in those cases? A command that downloads it and just prints out what extras are available?

[rbtcollins]

exactly

[dstufft]

Ok, we can keep this, but I'm going to fold it into #484.