Current File : //opt/alt/python33/share/doc/alt-python33-pip/docs/user_guide.rst
==========
User Guide
==========
.. contents::
Installing Packages
*******************
pip supports installing from `PyPI`_, version control, local projects, and
directly from distribution files.
The most common scenario is to install from `PyPI`_ using :ref:`Requirement
Specifiers`
::
$ pip install SomePackage # latest version
$ pip install SomePackage==1.0.4 # specific version
$ pip install 'SomePackage>=1.0.4' # minimum version
For more information and examples, see the :ref:`pip install` reference.
.. _`Requirements Files`:
Requirements Files
******************
"Requirements files" are files containing a list of items to be
installed using :ref:`pip install` like so:
::
pip install -r requirements.txt
Details on the format of the files are here: :ref:`Requirements File Format`.
Logically, a Requirements file is just a list of :ref:`pip install` arguments
placed in a file.
In practice, there are 4 common uses of Requirements files:
1. Requirements files are used to hold the result from :ref:`pip freeze` for the
purpose of achieving :ref:`repeatable installations <Repeatability>`. In
this case, your requirement file contains a pinned version of everything that
was installed when `pip freeze` was run.
::
pip freeze > requirements.txt
pip install -r requirements.txt
2. Requirements files are used to force pip to properly resolve dependencies.
As it is now, pip `doesn't have true dependency resolution
<https://github.com/pypa/pip/issues/988>`_, but instead simply uses the first
specification it finds for a project. E.g if `pkg1` requires `pkg3>=1.0` and
`pkg2` requires `pkg3>=1.0,<=2.0`, and if `pkg1` is resolved first, pip will
only use `pkg3>=1.0`, and could easily end up installing a version of `pkg3`
that conflicts with the needs of `pkg2`. To solve this problem, you can
place `pkg3>=1.0,<=2.0` (i.e. the correct specification) into your
requirements file directly along with the other top level requirements. Like
so:
::
pkg1
pkg2
pkg3>=1.0,<=2.0
3. Requirements files are used to force pip to install an alternate version of a
sub-dependency. For example, suppose `ProjectA` in your requirements file
requires `ProjectB`, but the latest version (v1.3) has a bug, you can force
pip to accept earlier versions like so:
::
ProjectA
ProjectB<1.3
4. Requirements files are used to override a dependency with a local patch that
lives in version control. For example, suppose a dependency,
`SomeDependency` from PyPI has a bug, and you can't wait for an upstream fix.
You could clone/copy the src, make the fix, and place it in vcs with the tag
`sometag`. You'd reference it in your requirements file with a line like so:
::
git+https://myvcs.com/some_dependency@sometag#egg=SomeDependency
If `SomeDependency` was previously a top-level requirement in your
requirements file, then **replace** that line with the new line. If
`SomeDependency` is a sub-dependency, then **add** the new line.
It's important to be clear that pip determines package dependencies using
`install_requires metadata
<http://pythonhosted.org/setuptools/setuptools.html#declaring-dependencies>`_,
not by discovering `requirements.txt` files embedded in projects.
See also:
* :ref:`Requirements File Format`
* :ref:`pip freeze`
* `"setup.py vs requirements.txt" (an article by Donald Stufft)
<https://caremad.io/blog/setup-vs-requirement/>`_
.. _`Installing from Wheels`:
Installing from Wheels
**********************
"Wheel" is a built, archive format that can greatly speed installation compared
to building and installing from source archives. For more information, see the
`Wheel docs <http://wheel.readthedocs.org>`_ ,
`PEP427 <http://www.python.org/dev/peps/pep-0427>`_, and
`PEP425 <http://www.python.org/dev/peps/pep-0425>`_
Pip prefers Wheels where they are available. To disable this, use the
:ref:`--no-use-wheel <install_--no-use-wheel>` flag for :ref:`pip install`.
If no satisfactory wheels are found, pip will default to finding source archives.
To install directly from a wheel archive:
::
pip install SomePackage-1.0-py2.py3-none-any.whl
For the cases where wheels are not available, pip offers :ref:`pip wheel` as a
convenience, to build wheels for all your requirements and dependencies.
:ref:`pip wheel` requires the `wheel package
<https://pypi.python.org/pypi/wheel>`_ to be installed, which provides the
"bdist_wheel" setuptools extension that it uses.
To build wheels for your requirements and all their dependencies to a local directory:
::
pip install wheel
pip wheel --wheel-dir=/local/wheels -r requirements.txt
And *then* to install those requirements just using your local directory of wheels (and not from PyPI):
::
pip install --no-index --find-links=/local/wheels -r requirements.txt
Uninstalling Packages
*********************
pip is able to uninstall most packages like so:
::
$ pip uninstall SomePackage
pip also performs an automatic uninstall of an old version of a package
before upgrading to a newer version.
For more information and examples, see the :ref:`pip uninstall` reference.
Listing Packages
****************
To list installed packages:
::
$ pip list
Pygments (1.5)
docutils (0.9.1)
Sphinx (1.1.2)
Jinja2 (2.6)
To list outdated packages, and show the latest version available:
::
$ pip list --outdated
docutils (Current: 0.9.1 Latest: 0.10)
Sphinx (Current: 1.1.2 Latest: 1.1.3)
To show details about an installed package:
::
$ pip show sphinx
---
Name: Sphinx
Version: 1.1.3
Location: /my/env/lib/pythonx.x/site-packages
Requires: Pygments, Jinja2, docutils
For more information and examples, see the :ref:`pip list` and :ref:`pip show`
reference pages.
Searching for Packages
**********************
pip can search `PyPI`_ for packages using the ``pip search``
command::
$ pip search "query"
The query will be used to search the names and summaries of all
packages.
For more information and examples, see the :ref:`pip search` reference.
.. _`Configuration`:
Configuration
*************
.. _config-file:
Config file
------------
pip allows you to set all command line option defaults in a standard ini
style config file.
The names and locations of the configuration files vary slightly across
platforms.
* On Unix and Mac OS X the configuration file is: :file:`$HOME/.pip/pip.conf`
* On Windows, the configuration file is: :file:`%HOME%\\pip\\pip.ini`
You can set a custom path location for the config file using the environment variable ``PIP_CONFIG_FILE``.
The names of the settings are derived from the long command line option, e.g.
if you want to use a different package index (``--index-url``) and set the
HTTP timeout (``--default-timeout``) to 60 seconds your config file would
look like this:
.. code-block:: ini
[global]
timeout = 60
index-url = http://download.zope.org/ppix
Each subcommand can be configured optionally in its own section so that every
global setting with the same name will be overridden; e.g. decreasing the
``timeout`` to ``10`` seconds when running the `freeze`
(`Freezing Requirements <./#freezing-requirements>`_) command and using
``60`` seconds for all other commands is possible with:
.. code-block:: ini
[global]
timeout = 60
[freeze]
timeout = 10
Boolean options like ``--ignore-installed`` or ``--no-dependencies`` can be
set like this:
.. code-block:: ini
[install]
ignore-installed = true
no-dependencies = yes
Appending options like ``--find-links`` can be written on multiple lines:
.. code-block:: ini
[global]
find-links =
http://download.example.com
[install]
find-links =
http://mirror1.example.com
http://mirror2.example.com
Environment Variables
---------------------
pip's command line options can be set with environment variables using the
format ``PIP_<UPPER_LONG_NAME>`` . Dashes (``-``) have to be replaced with
underscores (``_``).
For example, to set the default timeout::
export PIP_DEFAULT_TIMEOUT=60
This is the same as passing the option to pip directly::
pip --default-timeout=60 [...]
To set options that can be set multiple times on the command line, just add
spaces in between values. For example::
export PIP_FIND_LINKS="http://mirror1.example.com http://mirror2.example.com"
is the same as calling::
pip install --find-links=http://mirror1.example.com --find-links=http://mirror2.example.com
Config Precedence
-----------------
Command line options have precedence over environment variables, which have precedence over the config file.
Within the config file, command specific sections have precedence over the global section.
Examples:
- ``--host=foo`` overrides ``PIP_HOST=foo``
- ``PIP_HOST=foo`` overrides a config file with ``[global] host = foo``
- A command specific section in the config file ``[<command>] host = bar``
overrides the option with same name in the ``[global]`` config file section
Command Completion
------------------
pip comes with support for command line completion in bash and zsh.
To setup for bash::
$ pip completion --bash >> ~/.profile
To setup for zsh::
$ pip completion --zsh >> ~/.zprofile
Alternatively, you can use the result of the ``completion`` command
directly with the eval function of you shell, e.g. by adding the following to your startup file::
eval "`pip completion --bash`"
.. _`Fast & Local Installs`:
Fast & Local Installs
*********************
Often, you will want a fast install from local archives, without probing PyPI.
First, download the archives that fulfill your requirements::
$ pip install --download <DIR> -r requirements.txt
Then, install using :ref:`--find-links <--find-links>` and :ref:`--no-index <--no-index>`::
$ pip install --no-index --find-links=[file://]<DIR> -r requirements.txt
Non-recursive upgrades
************************
``pip install --upgrade`` is currently written to perform a recursive upgrade.
E.g. supposing:
* `SomePackage-1.0` requires `AnotherPackage>=1.0`
* `SomePackage-2.0` requires `AnotherPackage>=1.0` and `OneMorePoject==1.0`
* `SomePackage-1.0` and `AnotherPackage-1.0` are currently installed
* `SomePackage-2.0` and `AnotherPackage-2.0` are the latest versions available on PyPI.
Running ``pip install --upgrade SomePackage`` would upgrade `SomePackage` *and* `AnotherPackage`
despite `AnotherPackage` already being satisifed.
If you would like to perform a non-recursive upgrade perform these 2 steps::
pip install --upgrade --no-deps SomePackage
pip install SomePackage
The first line will upgrade `SomePackage`, but not dependencies like `AnotherPackage`. The 2nd line will fill in new dependencies like `OneMorePackage`.
User Installs
*************
With Python 2.6 came the `"user scheme" for installation
<http://docs.python.org/install/index.html#alternate-installation-the-user-scheme>`_,
which means that all Python distributions support an alternative install
location that is specific to a user. The default location for each OS is
explained in the python documentation for the `site.USER_BASE
<http://docs.python.org/library/site.html#site.USER_BASE>`_ variable. This mode
of installation can be turned on by specifying the :ref:`--user
<install_--user>` option to ``pip install``.
Moreover, the "user scheme" can be customized by setting the
``PYTHONUSERBASE`` environment variable, which updates the value of ``site.USER_BASE``.
To install "SomePackage" into an environment with site.USER_BASE customized to '/myappenv', do the following::
export PYTHONUSERBASE=/myappenv
pip install --user SomePackage
``pip install --user`` follows four rules:
#. When globally installed packages are on the python path, and they *conflict*
with the installation requirements, they are ignored, and *not*
uninstalled.
#. When globally installed packages are on the python path, and they *satisfy*
the installation requirements, pip does nothing, and reports that
requirement is satisfied (similar to how global packages can satisfy
requirements when installing packages in a ``--system-site-packages``
virtualenv).
#. pip will not perform a ``--user`` install in a ``--no-site-packages``
virtualenv (i.e. the default kind of virtualenv), due to the user site not
being on the python path. The installation would be pointless.
#. In a ``--system-site-packages`` virtualenv, pip will not install a package
that conflicts with a package in the virtualenv site-packages. The --user
installation would lack sys.path precedence and be pointless.
To make the rules clearer, here are some examples:
From within a ``--no-site-packages`` virtualenv (i.e. the default kind)::
$ pip install --user SomePackage
Can not perform a '--user' install. User site-packages are not visible in this virtualenv.
From within a ``--system-site-packages`` virtualenv where ``SomePackage==0.3`` is already installed in the virtualenv::
$ pip install --user SomePackage==0.4
Will not install to the user site because it will lack sys.path precedence
From within a real python, where ``SomePackage`` is *not* installed globally::
$ pip install --user SomePackage
[...]
Successfully installed SomePackage
From within a real python, where ``SomePackage`` *is* installed globally, but is *not* the latest version::
$ pip install --user SomePackage
[...]
Requirement already satisfied (use --upgrade to upgrade)
$ pip install --user --upgrade SomePackage
[...]
Successfully installed SomePackage
From within a real python, where ``SomePackage`` *is* installed globally, and is the latest version::
$ pip install --user SomePackage
[...]
Requirement already satisfied (use --upgrade to upgrade)
$ pip install --user --upgrade SomePackage
[...]
Requirement already up-to-date: SomePackage
# force the install
$ pip install --user --ignore-installed SomePackage
[...]
Successfully installed SomePackage
.. _`Repeatability`:
Ensuring Repeatability
**********************
Three things are required to fully guarantee a repeatable installation using requirements files.
1. The requirements file was generated by ``pip freeze`` or you're sure it only
contains requirements that specify a specific version.
2. The installation is performed using :ref:`--no-deps <install_--no-deps>`.
This guarantees that only what is explicitly listed in the requirements file is
installed.
3. The installation is performed against an index or find-links location that is
guaranteed to *not* allow archives to be changed and updated without a
version increase. Unfortunately, this is *not* true on PyPI. It is possible
for the same pypi distribution to have a different hash over time. Project
authors are allowed to delete a distribution, and then upload a new one with
the same name and version, but a different hash. See `Issue #1175
<https://github.com/pypa/pip/issues/1175>`_ for plans to add hash
confirmation to pip, or a new "lock file" notion, but for now, know that the `peep
project <https://pypi.python.org/pypi/peep>`_ offers this feature on top of pip
using requirements file comments.
.. _PyPI: http://pypi.python.org/pypi/
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