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2023-12-01

安装 package

pip 支持从 PyPI 、版本控制系统、本地项目, 甚至直接通过distribution文件安装package.

最常见的是使用 Requirement Specifiers 从 PyPI 安装。

$ pip install SomePackage            # 最新版本
$ pip install SomePackage==1.0.4     # 指定版本
$ pip install 'SomePackage>=1.0.4'     # 最低版本

更多详情可以参考 pip install 一节.

Requirements 文件

“Requirements 文件”中列出了需要安装的package，并可以通过 pip install 来安装:

pip install -r requirements.txt

这个文件的格式详情可以参考: Requirements File Format.

理论上来说，Requirements只是一个包含了由 pip install 参数排成列表的文件.

实践中，Requirements文件通常有4种作用:

pip freeze 输出的信息保存在Requirements文件中，主要用于 repeatable installations. In 在这种情况下，requirement文件会包含你运行 pip freeze 命令时各个package的版本信息.
```
pip freeze > requirements.txt
pip install -r requirements.txt
```
引导pip正确地安装满足需求的package. 由于现在pip 还不具备真正的依赖分析, 只是简单地为项目匹配第一需求. 举个例子：假如 pkg1 需要 pkg3>=1.0, pkg2 需要 pkg3>=1.0,<=2.0, 如果 pkg1 被先安装, 那么pip只会满足 pkg3>=1.0, 这样可能会导致所安装的 pkg3 版本和 pkg2 发生冲突. 如果要解决这个问题，需要把 pkg3>=1.0,<=2.0 (正确的指定) 写入 requirements 文件. 例如:
```
pkg1
pkg2
pkg3>=1.0,<=2.0
```
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
```
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, not by discovering requirements.txt files embedded in projects.

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 , PEP427, and PEP425

Pip prefers Wheels where they are available. To disable this, use the –no-use-wheel flag for 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 pip wheel as a convenience, to build wheels for all your requirements and dependencies.

pip wheel requires the wheel package 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 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 pip list and 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 pip search reference.

Configuration

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: $HOME/.pip/pip.conf
On Windows, the configuration file is: %HOME%\pip\pip.ini

You can set a custom path location for the config file using the environment variable PIP_CONFIG_FILE.

In a virtual environment, an additional config file will be read from the base directory of the virtualenv (sys.prefix as reported by Python). The base name of the file is the same as the user configuration file (pip.conf on Unix and OSX, pip.ini on Windows). Values in the virtualenv-specific configuration file take precedence over those in the user’s configuration file (whether from the user home or specified via 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:

[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) command and using 60 seconds for all other commands is possible with:

[global]
timeout = 60

[freeze]
timeout = 10

Boolean options like --ignore-installed or --no-dependencies can be set like this:

[install]
ignore-installed = true
no-dependencies = yes

Appending options like --find-links can be written on multiple lines:

[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

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 –find-links and –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, 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 variable. This mode of installation can be turned on by specifying the –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

Ensuring Repeatability

Three things are required to fully guarantee a repeatable installation using requirements files.

The requirements file was generated by pip freeze or you’re sure it only contains requirements that specify a specific version.
The installation is performed using –no-deps. This guarantees that only what is explicitly listed in the requirements file is installed.
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 for plans to add hash confirmation to pip, or a new “lock file” notion, but for now, know that the peep project offers this feature on top of pip using requirements file comments.