12.3. 使用pip管理包

你可以使用一个名为 pip 的程序来安装、升级和移除软件包。默认情况下 pip 将从 Python Package Index [https://pypi.org](https://pypi.org)\ 安装软件包。你可以在浏览器中访问 Python Package Index 或是使用 pip 受限的搜索功能:

  1. (tutorial-env) $ pip search astronomy
  2. skyfield               - Elegant astronomy for Python
  3. gary                   - Galactic astronomy and gravitational dynamics.
  4. novas                  - The United States Naval Observatory NOVAS astronomy library
  5. astroobs               - Provides astronomy ephemeris to plan telescope observations
  6. PyAstronomy            - A collection of astronomy related tools for Python.
  7. ...

pip 有许多子命令：“search”、“install”、“uninstall”、“freeze”等等。（请参阅 安装 Python 模块 指南以了解 pip 的完整文档。）

您可以通过指定包的名称来安装最新版本的包：

  1. (tutorial-env) $ python -m pip install novas
  2. Collecting novas
  3.   Downloading novas-3.1.1.3.tar.gz (136kB)
  4. Installing collected packages: novas
  5.   Running setup.py install for novas
  6. Successfully installed novas-3.1.1.3

您还可以通过提供包名称后跟 == 和版本号来安装特定版本的包：

  1. (tutorial-env) $ python -m pip install requests==2.6.0
  2. Collecting requests==2.6.0
  3.   Using cached requests-2.6.0-py2.py3-none-any.whl
  4. Installing collected packages: requests
  5. Successfully installed requests-2.6.0

如果你重新运行这个命令，pip 会注意到已经安装了所请求的版本并且什么都不做。您可以提供不同的版本号来获取该版本，或者您可以运行 pip install --upgrade 将软件包升级到最新版本：

  1. (tutorial-env) $ python -m pip install --upgrade requests
  2. Collecting requests
  3. Installing collected packages: requests
  4.   Found existing installation: requests 2.6.0
  5.     Uninstalling requests-2.6.0:
  6.       Successfully uninstalled requests-2.6.0
  7. Successfully installed requests-2.7.0

pip uninstall 后跟一个或多个包名称将从虚拟环境中删除包。

pip show 将显示有关特定包的信息：

  1. (tutorial-env) $ pip show requests
  2. ---
  3. Metadata-Version: 2.0
  4. Name: requests
  5. Version: 2.7.0
  6. Summary: Python HTTP for Humans.
  7. Home-page: http://python-requests.org
  8. Author: Kenneth Reitz
  9. Author-email: me@kennethreitz.com
  10. License: Apache 2.0
  11. Location: /Users/akuchling/envs/tutorial-env/lib/python3.4/site-packages
  12. Requires:

pip list 将显示虚拟环境中安装的所有软件包：

  1. (tutorial-env) $ pip list
  2. novas (3.1.1.3)
  3. numpy (1.9.2)
  4. pip (7.0.3)
  5. requests (2.7.0)
  6. setuptools (16.0)

pip freeze` 将生成一个类似的已安装包列表，但输出使用 pip install 期望的格式。一个常见的约定是将此列表放在 requirements.txt 文件中：

  1. (tutorial-env) $ pip freeze > requirements.txt
  2. (tutorial-env) $ cat requirements.txt
  3. novas==3.1.1.3
  4. numpy==1.9.2
  5. requests==2.7.0

然后可以将 requirements.txt 提交给版本控制并作为应用程序的一部分提供。然后用户可以使用 install -r 安装所有必需的包：

  1. (tutorial-env) $ python -m pip install -r requirements.txt
  2. Collecting novas==3.1.1.3 (from -r requirements.txt (line 1))
  3.   ...
  4. Collecting numpy==1.9.2 (from -r requirements.txt (line 2))
  5.   ...
  6. Collecting requests==2.7.0 (from -r requirements.txt (line 3))
  7.   ...
  8. Installing collected packages: novas, numpy, requests
  9.   Running setup.py install for novas
  10. Successfully installed novas-3.1.1.3 numpy-1.9.2 requests-2.7.0

pip 有更多选择。有关 pip 的完整文档，请参阅 安装 Python 模块 指南。当您编写一个包并希望在 Python 包索引中使它可用时，请参考 分发 Python 模块 指南。