Python VIRTUAL ENV
27 Nov 2017Python virtual enviroment 提供一个独立的 python 运行环境， 用来解决类似 Windows 上的 DLL HELL 问题。 将应用的依赖和版本等隔离开来。每个应用有自己的隔离环境。
Python 在用的版本有很多， 2.6， 2.7， 3.5， 3.6 等等。 每一个依赖也可能很多版本，中间很多兼容性问题。 如果将他们全都放到一起， 就会产生 DLL HELL 的问题。
➜ module2 l /usr/local/lib/python2.7/site-packages
total 4392
drwxr-xr-x 95 lucas admin 3.0K Nov 24 18:00 .
drwxr-xr-x 4 lucas admin 128B Nov 1 20:26 ..
drwxr-xr-x 9 lucas admin 288B Nov 3 23:25 astroid-1.5.3.dist-info
drwxr-xr-x 7 lucas admin 224B Nov 3 23:25 backports
drwxr-xr-x 9 lucas admin 288B Nov 3 23:25 backports.functools_lru_cache-1.4.dist-info
Install
$ [sudo] pip install virtualenv
也可以安装源代码到本地，这样不需要 sudo 权限
$ python virtualenv.py myVE
$ ls -lah
total 256K
drwxr-xr-x 10 lucas lucas 4.0K 2017-11-27 16:01 .
drwxr-xr-x 7 lucas lucas 4.0K 2017-11-27 16:01 ..
-rw-r--r-- 1 lucas lucas 1.2K 2016-11-16 11:39 AUTHORS.txt
drwxr-xr-x 2 lucas lucas 4.0K 2016-11-16 11:39 bin
drwxr-xr-x 2 lucas lucas 4.0K 2016-11-16 11:39 docs
-rw-r--r-- 1 lucas lucas 1.2K 2016-11-16 11:39 LICENSE.txt
-rw-r--r-- 1 lucas lucas 345 2016-11-16 11:39 MANIFEST.in
drwxr-xr-x 5 lucas lucas 4.0K 2017-11-27 16:01 myVE
-rw-r--r-- 1 lucas lucas 3.4K 2016-11-16 11:39 PKG-INFO
-rw-r--r-- 1 lucas lucas 1.2K 2016-11-16 11:39 README.rst
drwxr-xr-x 2 lucas lucas 4.0K 2016-11-16 11:39 scripts
-rw-r--r-- 1 lucas lucas 88 2016-11-16 11:39 setup.cfg
-rw-r--r-- 1 lucas lucas 4.0K 2016-11-16 11:39 setup.py
drwxr-xr-x 2 lucas lucas 4.0K 2016-11-16 11:39 tests
drwxr-xr-x 2 lucas lucas 4.0K 2016-11-16 11:39 virtualenv.egg-info
drwxr-xr-x 2 lucas lucas 4.0K 2016-11-16 11:39 virtualenv_embedded
-rwxr-xr-x 1 lucas lucas 97K 2016-11-16 11:39 virtualenv.py
-rw-r--r-- 1 lucas lucas 86K 2017-11-27 16:01 virtualenv.pyc
drwxr-xr-x 2 lucas lucas 4.0K 2016-11-16 11:39 virtualenv_support
核心文件是virtualenv.py
当然要求 相关的类库存在。
使用
➜ /tmp virtualenv ENV
New python executable in /private/tmp/ENV/bin/python2.7
Also creating executable in /private/tmp/ENV/bin/python
Installing setuptools, pip, wheel...done.
➜ /tmp tree -L 2 ENV
ENV
├── bin
│ ├── activate
│ ├── activate.csh
│ ├── activate.fish
│ ├── activate_this.py
│ ├── easy_install
│ ├── easy_install-2.7
│ ├── pip
│ ├── pip2
│ ├── pip2.7
│ ├── python -> python2.7
│ ├── python-config
│ ├── python2 -> python2.7
│ ├── python2.7
│ └── wheel
├── include
│ └── python2.7 -> /usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/include/python2.7
├── lib
│ └── python2.7
└── pip-selfcheck.json
5 directories, 15 files
- ENV/lib/ and ENV/include/ are created, containing supporting library files for a new virtualenv python. Packages installed in this environment will live under ENV/lib/pythonX.X/site-packages/.
- ENV/bin is created, where executables live - noticeably a new python. Thus running a script with #! /path/to/ENV/bin/python would run that script under this virtualenv’s python.
- The crucial packages pip and setuptools are installed, which allow other packages to be easily installed to the environment. This associated pip can be run from ENV/bin/pip.
激活
$ source bin/activate
``` $ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
$ source bin/activate
$ echo $PATH /home/xx/virtualenv-15.1.0/myVE/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games