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pip install

Usage

install

Description

install

Overview

Pip install has several stages:

  1. Resolve dependencies. What will be installed is determined here.
  2. Build wheels. All the dependencies that can be are built into wheels.
  3. Install the packages (and uninstall anything being upgraded/replaced).

Installation Order

As of v6.1.0, pip installs dependencies before their dependents, i.e. in "topological order". This is the only commitment pip currently makes related to order. While it may be coincidentally true that pip will install things in the order of the install arguments or in the order of the items in a requirements file, this is not a promise.

In the event of a dependency cycle (aka "circular dependency"), the current implementation (which might possibly change later) has it such that the first encountered member of the cycle is installed last.

For instance, if quux depends on foo which depends on bar which depends on baz, which depends on foo:

pip install quux
...
Installing collected packages baz, bar, foo, quux

pip install bar
...
Installing collected packages foo, baz, bar

Prior to v6.1.0, pip made no commitments about install order.

The decision to install topologically is based on the principle that installations should proceed in a way that leaves the environment usable at each step. This has two main practical benefits:

  1. Concurrent use of the environment during the install is more likely to work.
  2. A failed install is less likely to leave a broken environment. Although pip would like to support failure rollbacks eventually, in the mean time, this is an improvement.

Although the new install order is not intended to replace (and does not replace) the use of setup_requires to declare build dependencies, it may help certain projects install from sdist (that might previously fail) that fit the following profile:

  1. They have build dependencies that are also declared as install dependencies using install_requires.
  2. python setup.py egg_info works without their build dependencies being installed.
  3. For whatever reason, they don't or won't declare their build dependencies using setup_requires.

Requirements File Format

Each line of the requirements file indicates something to be installed, and like arguments to pip install, the following forms are supported:

[[--option]...]
<requirement specifier> [; markers] [[--option]...]
<archive url/path>
[-e] <local project path>
[-e] <vcs project url>

For details on requirement specifiers, see Requirement Specifiers.

See the pip install Examples<pip install Examples> for examples of all these forms.

A line that begins with # is treated as a comment and ignored. Whitespace followed by a # causes the # and the remainder of the line to be treated as a comment.

A line ending in an unescaped \ is treated as a line continuation and the newline following it is effectively ignored.

Comments are stripped before line continuations are processed.

Additionally, the following Package Index Options are supported:

  • -i, --index-url <--index-url>
  • --extra-index-url <--extra-index-url>
  • --no-index <--no-index>
  • -f, --find-links <--find-links>
  • --no-binary <install_--no-binary>
  • --only-binary <install_--only-binary>

For example, to specify --no-index <--no-index> and 2 --find-links <--find-links> locations:

--no-index
--find-links /my/local/archives
--find-links http://some.archives.com/archives

If you wish, you can refer to other requirements files, like this:

-r more_requirements.txt

You can also refer to constraints files <Constraints Files>, like this:

-c some_constraints.txt

Example Requirements File

Use pip install -r example-requirements.txt to install:

#
####### example-requirements.txt #######
#
###### Requirements without Version Specifiers ######
nose
nose-cov
beautifulsoup4
#
###### Requirements with Version Specifiers ######
#   See https://www.python.org/dev/peps/pep-0440/#version-specifiers
docopt == 0.6.1             # Version Matching. Must be version 0.6.1
keyring >= 4.1.1            # Minimum version 4.1.1
coverage != 3.5             # Version Exclusion. Anything except version 3.5
Mopidy-Dirble ~= 1.1        # Compatible release. Same as >= 1.1, == 1.1.*
#
###### Refer to other requirements files ######
-r other-requirements.txt
#
#
###### A particular file ######
./downloads/numpy-1.9.2-cp34-none-win32.whl
http://wxpython.org/Phoenix/snapshot-builds/wxPython_Phoenix-3.0.3.dev1820+49a8884-cp34-none-win_amd64.whl
#
###### Additional Requirements without Version Specifiers ######
#   Same as 1st section, just here to show that you can put things in any order.
rejected
green
#

Requirement Specifiers

pip supports installing from a package index using a requirement specifier <pypug:Requirement Specifier>. Generally speaking, a requirement specifier is composed of a project name followed by optional version specifiers <pypug:Version Specifier>. PEP440 <pypa:PEP440s> contains a full specification of the currently supported specifiers.

Some examples:

SomeProject
SomeProject == 1.3
SomeProject >=1.2,<.2.0
SomeProject[foo, bar]
SomeProject~=1.4.2

Since version 6.0, pip also supports specifers containing environment markers like so:

SomeProject ==5.4 ; python_version < '2.7'
SomeProject; sys.platform == 'win32'

Environment markers are supported in the command line and in requirements files.

Note

Use quotes around specifiers in the shell when using >, <, or when using environment markers. Don't use quotes in requirement files.1

Per-requirement Overrides

Since version 7.0 pip supports controlling the command line options given to setup.py via requirements files. This disables the use of wheels (cached or otherwise) for that package, as setup.py does not exist for wheels.

The --global-option and --install-option options are used to pass options to setup.py. For example:

FooProject >= 1.2 --global-option="--no-user-cfg" \
                  --install-option="--prefix='/usr/local'" \
                  --install-option="--no-compile"

The above translates roughly into running FooProject's setup.py script as:

python setup.py --no-user-cfg install --prefix='/usr/local' --no-compile

Note that the only way of giving more than one option to setup.py is through multiple --global-option and --install-option options, as shown in the example above. The value of each option is passed as a single argument to the setup.py script. Therefore, a line such as the following is invalid and would result in an installation error.

# Invalid. Please use '--install-option' twice as shown above.
FooProject >= 1.2 --install-option="--prefix=/usr/local --no-compile"

Pre-release Versions

Starting with v1.4, pip will only install stable versions as specified by PEP426 by default. If a version cannot be parsed as a compliant PEP426 version then it is assumed to be a pre-release.

If a Requirement specifier includes a pre-release or development version (e.g. >=0.0.dev0) then pip will allow pre-release and development versions for that requirement. This does not include the != flag.

The pip install command also supports a --pre <install_--pre> flag that will enable installing pre-releases and development releases.

VCS Support

pip supports installing from Git, Mercurial, Subversion and Bazaar, and detects the type of VCS using url prefixes: "git+", "hg+", "bzr+", "svn+".

pip requires a working VCS command on your path: git, hg, svn, or bzr.

VCS projects can be installed in editable mode <editable-installs> (using the --editable <install_--editable> option) or not.

  • For editable installs, the clone location by default is "<venv path>/src/SomeProject" in virtual environments, and "<cwd>/src/SomeProject" for global installs. The --src <install_--src> option can be used to modify this location.
  • For non-editable installs, the project is built locally in a temp dir and then installed normally.

The "project name" component of the url suffix "egg=<project name>-<version>" is used by pip in its dependency logic to identify the project prior to pip downloading and analyzing the metadata. The optional "version" component of the egg name is not functionally important. It merely provides a human-readable clue as to what version is in use. For projects where setup.py is not in the root of project, "subdirectory" component is used. Value of "subdirectory" component should be a path starting from root of the project to where setup.py is located.

Git

pip currently supports cloning over git, git+https and git+ssh:

Here are the supported forms:

[-e] git+git://git.myproject.org/MyProject#egg=MyProject
[-e] git+https://git.myproject.org/MyProject#egg=MyProject
[-e] git+ssh://git.myproject.org/MyProject#egg=MyProject
-e git+git@git.myproject.org:MyProject#egg=MyProject

Passing branch names, a commit hash or a tag name is possible like so:

[-e] git://git.myproject.org/MyProject.git@master#egg=MyProject
[-e] git://git.myproject.org/MyProject.git@v1.0#egg=MyProject
[-e] git://git.myproject.org/MyProject.git@da39a3ee5e6b4b0d3255bfef95601890afd80709#egg=MyProject

Mercurial

The supported schemes are: hg+http, hg+https, hg+static-http and hg+ssh.

Here are the supported forms:

[-e] hg+http://hg.myproject.org/MyProject#egg=MyProject
[-e] hg+https://hg.myproject.org/MyProject#egg=MyProject
[-e] hg+ssh://hg.myproject.org/MyProject#egg=MyProject

You can also specify a revision number, a revision hash, a tag name or a local branch name like so:

[-e] hg+http://hg.myproject.org/MyProject@da39a3ee5e6b#egg=MyProject
[-e] hg+http://hg.myproject.org/MyProject@2019#egg=MyProject
[-e] hg+http://hg.myproject.org/MyProject@v1.0#egg=MyProject
[-e] hg+http://hg.myproject.org/MyProject@special_feature#egg=MyProject

Subversion

pip supports the URL schemes svn, svn+svn, svn+http, svn+https, svn+ssh.

You can also give specific revisions to an SVN URL, like so:

[-e] svn+svn://svn.myproject.org/svn/MyProject#egg=MyProject
[-e] svn+http://svn.myproject.org/svn/MyProject/trunk@2019#egg=MyProject

which will check out revision 2019. @{20080101} would also check out the revision from 2008-01-01. You can only check out specific revisions using -e svn+....

Bazaar

pip supports Bazaar using the bzr+http, bzr+https, bzr+ssh, bzr+sftp, bzr+ftp and bzr+lp schemes.

Here are the supported forms:

[-e] bzr+http://bzr.myproject.org/MyProject/trunk#egg=MyProject
[-e] bzr+sftp://user@myproject.org/MyProject/trunk#egg=MyProject
[-e] bzr+ssh://user@myproject.org/MyProject/trunk#egg=MyProject
[-e] bzr+ftp://user@myproject.org/MyProject/trunk#egg=MyProject
[-e] bzr+lp:MyProject#egg=MyProject

Tags or revisions can be installed like so:

[-e] bzr+https://bzr.myproject.org/MyProject/trunk@2019#egg=MyProject
[-e] bzr+http://bzr.myproject.org/MyProject/trunk@v1.0#egg=MyProject

Finding Packages

pip searches for packages on PyPI using the http simple interface, which is documented here and there

pip offers a number of Package Index Options for modifying how packages are found.

See the pip install Examples<pip install Examples>.

SSL Certificate Verification

Starting with v1.3, pip provides SSL certificate verification over https, for the purpose of providing secure, certified downloads from PyPI.

Caching

Starting with v6.0, pip provides an on by default cache which functions similarly to that of a web browser. While the cache is on by default and is designed do the right thing by default you can disable the cache and always access PyPI by utilizing the --no-cache-dir option.

When making any HTTP request pip will first check its local cache to determine if it has a suitable response stored for that request which has not expired. If it does then it simply returns that response and doesn't make the request.

If it has a response stored, but it has expired, then it will attempt to make a conditional request to refresh the cache which will either return an empty response telling pip to simply use the cached item (and refresh the expiration timer) or it will return a whole new response which pip can then store in the cache.

When storing items in the cache, pip will respect the CacheControl header if it exists, or it will fall back to the Expires header if that exists. This allows pip to function as a browser would, and allows the index server to communicate to pip how long it is reasonable to cache any particular item.

While this cache attempts to minimize network activity, it does not prevent network access altogether. If you want a local install solution that circumvents accessing PyPI, see Installing from local packages.

The default location for the cache directory depends on the Operating System:

Unix

~/.cache/pip and it respects the XDG_CACHE_HOME directory.

OS X

~/Library/Caches/pip.

Windows

<CSIDL_LOCAL_APPDATA>\\pip\\Cache

Wheel cache

Pip will read from the subdirectory wheels within the pip cache dir and use any packages found there. This is disabled via the same no-cache-dir option that disables the HTTP cache. The internal structure of that cache is not part of the pip API. As of 7.0 pip uses a subdirectory per sdist that wheels were built from, and wheels within that subdirectory.

Pip attempts to choose the best wheels from those built in preference to building a new wheel. Note that this means when a package has both optional C extensions and builds py tagged wheels when the C extension can't be built that pip will not attempt to build a better wheel for Pythons that would have supported it, once any generic wheel is built. To correct this, make sure that the wheels are built with Python specific tags - e.g. pp on Pypy.

When no wheels are found for an sdist, pip will attempt to build a wheel automatically and insert it into the wheel cache.

Hash Verification

PyPI provides md5 hashes in the hash fragment of package download urls.

pip supports checking this, as well as any of the guaranteed hashlib algorithms (sha1, sha224, sha384, sha256, sha512, md5).

The hash fragment is case sensitive (i.e. sha1 not SHA1).

This check is only intended to provide basic download corruption protection. It is not intended to provide security against tampering. For that, see SSL Certificate Verification

"Editable" Installs

"Editable" installs are fundamentally "setuptools develop mode" installs.

You can install local projects or VCS projects in "editable" mode:

$ pip install -e path/to/SomeProject
$ pip install -e git+http://repo/my_project.git#egg=SomeProject

(See the VCS Support section above for more information on VCS-related syntax.)

For local projects, the "SomeProject.egg-info" directory is created relative to the project path. This is one advantage over just using setup.py develop, which creates the "egg-info" directly relative the current working directory.

Controlling setup_requires

Setuptools offers the setup_requires setup() keyword for specifying dependencies that need to be present in order for the setup.py script to run. Internally, Setuptools uses easy_install to fulfill these dependencies.

pip has no way to control how these dependencies are located. None of the Package Index Options have an effect.

The solution is to configure a "system" or "personal" Distutils configuration file to manage the fulfillment.

For example, to have the dependency located at an alternate index, add this:

[easy_install]
index_url = https://my.index-mirror.com

To have the dependency located from a local directory and not crawl PyPI, add this:

[easy_install]
allow_hosts = ''
find_links = file:///path/to/local/archives

Build System Interface

In order for pip to install a package from source, setup.py must implement the following commands:

setup.py egg_info [--egg-base XXX]
setup.py install --record XXX [--single-version-externally-managed] [--root XXX] [--compile|--no-compile] [--install-headers XXX]

The egg_info command should create egg metadata for the package, as described in the setuptools documentation at http://pythonhosted.org/setuptools/setuptools.html#egg-info-create-egg-metadata-and-set-build-tags

The install command should implement the complete process of installing the package to the target directory XXX.

To install a package in "editable" mode (pip install -e), setup.py must implement the following command:

setup.py develop --no-deps

This should implement the complete process of installing the package in "editable" mode.

All packages will be attempted to built into wheels:

setup.py bdist_wheel -d XXX

One further setup.py command is invoked by pip install:

setup.py clean

This command is invoked to clean up temporary commands from the build. (TODO: Investigate in more detail when this command is required).

No other build system commands are invoked by the pip install command.

Installing a package from a wheel does not invoke the build system at all.

Options

install

Examples

  1. Install SomePackage and its dependencies from PyPI using Requirement Specifiers
$ pip install SomePackage            # latest version
$ pip install SomePackage==1.0.4     # specific version
$ pip install 'SomePackage>=1.0.4'     # minimum version
  1. Install a list of requirements specified in a file. See the Requirements files <Requirements Files>.
$ pip install -r requirements.txt
  1. Upgrade an already installed SomePackage to the latest from PyPI.
$ pip install --upgrade SomePackage
  1. Install a local project in "editable" mode. See the section on Editable Installs <editable-installs>.
$ pip install -e .                     # project in current directory
$ pip install -e path/to/project       # project in another directory
  1. Install a project from VCS in "editable" mode. See the sections on VCS Support <VCS Support> and Editable Installs <editable-installs>.
$ pip install -e git+https://git.repo/some_pkg.git#egg=SomePackage          # from git
$ pip install -e hg+https://hg.repo/some_pkg.git#egg=SomePackage            # from mercurial
$ pip install -e svn+svn://svn.repo/some_pkg/trunk/#egg=SomePackage         # from svn
$ pip install -e git+https://git.repo/some_pkg.git@feature#egg=SomePackage  # from 'feature' branch
$ pip install -e git+https://git.repo/some_repo.git#egg=subdir&subdirectory=subdir_path # install a python package from a repo subdirectory
  1. Install a package with setuptools extras.
$ pip install SomePackage[PDF]
$ pip install SomePackage[PDF]==3.0
$ pip install -e .[PDF]==3.0  # editable project in current directory
  1. Install a particular source archive file.
$ pip install ./downloads/SomePackage-1.0.4.tar.gz
$ pip install http://my.package.repo/SomePackage-1.0.4.zip
  1. Install from alternative package repositories.

Install from a different index, and not PyPI :

$ pip install --index-url http://my.package.repo/simple/ SomePackage

Search an additional index during install, in addition to PyPI :

$ pip install --extra-index-url http://my.package.repo/simple SomePackage

Install from a local flat directory containing archives (and don't scan indexes):

$ pip install --no-index --find-links=file:///local/dir/ SomePackage
$ pip install --no-index --find-links=/local/dir/ SomePackage
$ pip install --no-index --find-links=relative/dir/ SomePackage
  1. Find pre-release and development versions, in addition to stable versions. By default, pip only finds stable versions.
$ pip install --pre SomePackage

  1. This is true with the exception that pip v7.0 and v7.0.1 required quotes around specifiers containing environment markers in requirement files.↩