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author | Matt A. Tobin <mattatobin@localhost.localdomain> | 2018-02-02 04:16:08 -0500 |
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committer | Matt A. Tobin <mattatobin@localhost.localdomain> | 2018-02-02 04:16:08 -0500 |
commit | 5f8de423f190bbb79a62f804151bc24824fa32d8 (patch) | |
tree | 10027f336435511475e392454359edea8e25895d /testing/mozharness/external_tools/virtualenv/docs/index.rst | |
parent | 49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff) | |
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Add m-esr52 at 52.6.0
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diff --git a/testing/mozharness/external_tools/virtualenv/docs/index.rst b/testing/mozharness/external_tools/virtualenv/docs/index.rst new file mode 100644 index 000000000..e745a87b7 --- /dev/null +++ b/testing/mozharness/external_tools/virtualenv/docs/index.rst @@ -0,0 +1,137 @@ +Virtualenv +========== + +`Mailing list <http://groups.google.com/group/python-virtualenv>`_ | +`Issues <https://github.com/pypa/virtualenv/issues>`_ | +`Github <https://github.com/pypa/virtualenv>`_ | +`PyPI <https://pypi.python.org/pypi/virtualenv/>`_ | +User IRC: #pypa +Dev IRC: #pypa-dev + +Introduction +------------ + +``virtualenv`` is a tool to create isolated Python environments. + +The basic problem being addressed is one of dependencies and versions, +and indirectly permissions. Imagine you have an application that +needs version 1 of LibFoo, but another application requires version +2. How can you use both these applications? If you install +everything into ``/usr/lib/python2.7/site-packages`` (or whatever your +platform's standard location is), it's easy to end up in a situation +where you unintentionally upgrade an application that shouldn't be +upgraded. + +Or more generally, what if you want to install an application *and +leave it be*? If an application works, any change in its libraries or +the versions of those libraries can break the application. + +Also, what if you can't install packages into the global +``site-packages`` directory? For instance, on a shared host. + +In all these cases, ``virtualenv`` can help you. It creates an +environment that has its own installation directories, that doesn't +share libraries with other virtualenv environments (and optionally +doesn't access the globally installed libraries either). + +.. comment: split here + +.. toctree:: + :maxdepth: 2 + + installation + userguide + reference + development + changes + +.. warning:: + + Python bugfix releases 2.6.8, 2.7.3, 3.1.5 and 3.2.3 include a change that + will cause "import random" to fail with "cannot import name urandom" on any + virtualenv created on a Unix host with an earlier release of Python + 2.6/2.7/3.1/3.2, if the underlying system Python is upgraded. This is due to + the fact that a virtualenv uses the system Python's standard library but + contains its own copy of the Python interpreter, so an upgrade to the system + Python results in a mismatch between the version of the Python interpreter + and the version of the standard library. It can be fixed by removing + ``$ENV/bin/python`` and re-running virtualenv on the same target directory + with the upgraded Python. + +Other Documentation and Links +----------------------------- + +* `Blog announcement of virtualenv`__. + + .. __: http://blog.ianbicking.org/2007/10/10/workingenv-is-dead-long-live-virtualenv/ + +* James Gardner has written a tutorial on using `virtualenv with + Pylons + <http://wiki.pylonshq.com/display/pylonscookbook/Using+a+Virtualenv+Sandbox>`_. + +* Chris Perkins created a `showmedo video including virtualenv + <http://showmedo.com/videos/video?name=2910000&fromSeriesID=291>`_. + +* Doug Hellmann's `virtualenvwrapper`_ is a useful set of scripts to make + your workflow with many virtualenvs even easier. `His initial blog post on it`__. + He also wrote `an example of using virtualenv to try IPython`__. + + .. _virtualenvwrapper: https://pypi.python.org/pypi/virtualenvwrapper/ + .. __: https://doughellmann.com/blog/2008/05/01/virtualenvwrapper/ + .. __: https://doughellmann.com/blog/2008/02/01/ipython-and-virtualenv/ + +* `Pew`_ is another wrapper for virtualenv that makes use of a different + activation technique. + + .. _Pew: https://pypi.python.org/pypi/pew/ + +* `Using virtualenv with mod_wsgi + <http://code.google.com/p/modwsgi/wiki/VirtualEnvironments>`_. + +* `virtualenv commands + <https://github.com/thisismedium/virtualenv-commands>`_ for some more + workflow-related tools around virtualenv. + +* PyCon US 2011 talk: `Reverse-engineering Ian Bicking's brain: inside pip and virtualenv + <http://pyvideo.org/video/568/reverse-engineering-ian-bicking--39-s-brain--insi>`_. + By the end of the talk, you'll have a good idea exactly how pip + and virtualenv do their magic, and where to go looking in the source + for particular behaviors or bug fixes. + +Compare & Contrast with Alternatives +------------------------------------ + +There are several alternatives that create isolated environments: + +* ``workingenv`` (which I do not suggest you use anymore) is the + predecessor to this library. It used the main Python interpreter, + but relied on setting ``$PYTHONPATH`` to activate the environment. + This causes problems when running Python scripts that aren't part of + the environment (e.g., a globally installed ``hg`` or ``bzr``). It + also conflicted a lot with Setuptools. + +* `virtual-python + <http://peak.telecommunity.com/DevCenter/EasyInstall#creating-a-virtual-python>`_ + is also a predecessor to this library. It uses only symlinks, so it + couldn't work on Windows. It also symlinks over the *entire* + standard library and global ``site-packages``. As a result, it + won't see new additions to the global ``site-packages``. + + This script only symlinks a small portion of the standard library + into the environment, and so on Windows it is feasible to simply + copy these files over. Also, it creates a new/empty + ``site-packages`` and also adds the global ``site-packages`` to the + path, so updates are tracked separately. This script also installs + Setuptools automatically, saving a step and avoiding the need for + network access. + +* `zc.buildout <http://pypi.python.org/pypi/zc.buildout>`_ doesn't + create an isolated Python environment in the same style, but + achieves similar results through a declarative config file that sets + up scripts with very particular packages. As a declarative system, + it is somewhat easier to repeat and manage, but more difficult to + experiment with. ``zc.buildout`` includes the ability to setup + non-Python systems (e.g., a database server or an Apache instance). + +I *strongly* recommend anyone doing application development or +deployment use one of these tools. |