Python软件包

使用pip管理包

pip 是 Python 的一个包管理工具，用于安装、升级和移除软件包。pip 默认从 Python Package Index（PyPI）安装软件包，可以在浏览器中访问 PyPI 来查看可用的软件包。除了安装软件包之外，pip 还提供了许多其他命令，例如子命令: "install", "uninstall", "freeze" 等等。

通过指定包的名称来安装最新版本的包：

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

通过提供包名称后跟 == 和版本号来安装特定版本的包：

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

如果重新运行这个命令，pip 会注意到已经安装了所请求的版本因而不做任何事。 可以提供不同的版本号来获取相应版本，或者可以运行 python -m pip install --upgrade 以将软件包升级到最新版本:

(tutorial-env) $ python -m pip install --upgrade requests
Collecting requests
Installing collected packages: requests
Found existing installation: requests 2.6.0
Uninstalling requests-2.6.0:
Successfully uninstalled requests-2.6.0
Successfully installed requests-2.7.0

python -m pip uninstall 后跟一个或多个要从虚拟环境中删除的包所对应的名称。

python -m pip show 将显示有关某个特定包的信息:

(tutorial-env) $ python -m pip show requests
---
Metadata-Version: 2.0
Name: requests
Version: 2.7.0
Summary: Python HTTP for Humans.
Home-page: http://python-requests.org
Author: Kenneth Reitz
Author-email: me@kennethreitz.com
License: Apache 2.0
Location: /Users/akuchling/envs/tutorial-env/lib/python3.4/site-packages
Requires:

python -m pip list 将显示所有在虚拟环境中安装的包:

(tutorial-env) $ python -m pip list
novas (3.1.1.3)
numpy (1.9.2)
pip (7.0.3)
requests (2.7.0)
setuptools (16.0)

python -m pip freeze 将产生一个类似的已安装包列表，但其输出会使用 python -m pip install 所期望的格式。 一个常见的约定是将此列表放在 requirements.txt 文件中:

(tutorial-env) $ python -m pip freeze > requirements.txt
(tutorial-env) $ cat requirements.txt
novas==3.1.1.3
numpy==1.9.2
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：

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