Go to Python virtualenv

Python virtualenv [10:14:13 | Author: yuyun] font size: large | medium | small virtualenv serves as sandbox, it implements multiple independent virtual environments by isolating the package directory and system environment parameters. This prevents too many third-party libraries from issues caused by version dependencies. At the same time, each independent virtual environment can be distributed by packaging, which greatly facilitates system deployment.

$ sudo easy_install virtualenv

Now we can create a virtual environment.

$ virtualenv test1New python executable in test1/bin/pythonInstalling setuptools............done.

We can see that the basic running environment has been installed in the virtual directory.

$ ls test1/binactivate  activate_this.py  easy_install  easy_install-2.6  pip  python$ ls test1/include/python2.6$ ls test1/libpython2.6$ ls test1/lib/python2.6/_abcoll.py   copy_reg.pyc     linecache.py     os.pyc         sre_compile.py     stat.py_abcoll.pyc  distutils        linecache.pyc    posixpath.py   sre_compile.pyc    stat.pycabc.py       encodings        locale.py        posixpath.pyc  sre_constants.py   types.pyabc.pyc      fnmatch.py       locale.pyc       re.py          sre_constants.pyc  types.pyccodecs.py    fnmatch.pyc      ntpath.py        re.pyc         sre_parse.py       UserDict.pycodecs.pyc   genericpath.py   ntpath.pyc       site-packages  sre_parse.pyc      UserDict.pycconfig       genericpath.pyc  orig-prefix.txt  site.py        sre.py             warnings.pycopy_reg.py  lib-dynload      os.py            site.pyc       sre.pyc            warnings.pyc

Go to the test1 directory and activate the virtual environment.

$ cd test1test1$ source bin/activate(test)test1$ which python/home/yuhen/projects/test1/bin/python(test)test1$ which easy_install/home/yuhen/projects/test1/bin/easy_install(test1)test1$ pythonPython 2.6.5 (r265:79063, Apr 16 2010, 13:57:41)[GCC 4.4.3] on linux2Type "help", "copyright", "credits" or "license" for more information.>>> import sys>>> sys.path['', '/home/yuhen/projects/test1/lib/python2.6/site-packages/setuptools-0.6c11-py2.6.egg', '/home/yuhen/projects/test1/lib/python2.6/site-packages/pip-0.7.2-py2.6.egg', '/home/yuhen/projects/test1/lib/python2.6', '/home/yuhen/projects/test1/lib/python2.6/plat-linux2', '/home/yuhen/projects/test1/lib/python2.6/lib-tk', '/home/yuhen/projects/test1/lib/python2.6/lib-old', '/home/yuhen/projects/test1/lib/python2.6/lib-dynload', '/usr/lib/python2.6', '/usr/lib64/python2.6', '/usr/lib/python2.6/plat-linux2', '/usr/lib/python2.6/lib-tk', '/usr/lib64/python2.6/lib-tk', '/home/yuhen/projects/test1/lib/python2.6/site-packages', '/usr/local/lib/python2.6/dist-packages/virtualenv-1.4.9-py2.6.egg', '/usr/local/lib/python2.6/dist-packages/simplejson-2.1.1-py2.6-linux-x86_64.egg', '/usr/local/lib/python2.6/site-packages', '/usr/local/lib/python2.6/dist-packages', '/usr/lib/python2.6/dist-packages', '/usr/lib/pymodules/python2.6', '/usr/lib/pymodules/python2.6/gtk-2.0', '/usr/lib/python2.6/dist-packages/wx-2.8-gtk2-unicode']>>>

After "Souce bin/active" is activated, the command prompts that the line has an additional "(test1)" prefix. By default, Python and easy_install use programs in the bin directory of the virtual environment. SYS. Path: the Library directory of the current virtual environment is added to the search path list.

(test1)$ easy_install MySQL-pythonSearching for MySQL-pythonReading http://pypi.python.org/simple/MySQL-python/Reading http://sourceforge.net/projects/mysql-pythonBest match: MySQL-python 1.2.3c1Downloading http://sourceforge.net/.../1.2.3c1/MySQL-python-1.2.3c1.tar.gz/downloadProcessing downloadRunning MySQL-python-1.2.3c1/setup.py -q bdist_egg --dist-dir /tmp/easy_install-Em0wfb/MySQL-python-1.2.3c1/egg-dist-tmp-vzoJ2tIn file included from _mysql.c:36:/usr/include/mysql/my_config.h:1050:1: warning: "HAVE_WCSCOLL" redefinedIn file included from /usr/include/python2.6/Python.h:8,                 from pymemcompat.h:10,                 from _mysql.c:29:/usr/include/python2.6/pyconfig.h:808:1: warning: this is the location of the previous definitionzip_safe flag not set; analyzing archive contents...Adding MySQL-python 1.2.3c1 to easy-install.pth fileInstalled /home/yuhen/projects/python/test1/lib/python2.6/site-packages/MySQL_python-1.2.3c1-py2.6-linux-x86_64.eggProcessing dependencies for MySQL-pythonFinished processing dependencies for MySQL-python(test1)$ ls -l lib/python2.6/site-packages/total 444-rw-r--r-- 1 yuhen yuhen    283 2010-06-02 09:46 easy-install.pth-rw-r--r-- 1 yuhen yuhen 106325 2010-06-02 09:46 MySQL_python-1.2.3c1-py2.6-linux-x86_64.eggdrwxr-xr-x 4 yuhen yuhen   4096 2010-06-02 09:45 pip-0.7.2-py2.6.egg-rw-r--r-- 1 yuhen yuhen 333447 2010-06-01 23:58 setuptools-0.6c11-py2.6.egg-rw-r--r-- 1 yuhen yuhen     30 2010-06-02 09:45 setuptools.pth(test1)$ cat lib/python2.6/site-packages/setuptools.pth./setuptools-0.6c11-py2.6.egg(test1)$ python>>> import MySQLdb>>> MySQLdb.version_info(1, 2, 3, 'gamma', 1)>>>

Mysql-python is installed in a virtual environment and the egg search path is correctly added to the easy-install.pth.

Finally, we can use the "deactivate" command to exit the virtual environment.

(test1)test1$ deactivate

When creating a virtual environment, we can add the "-- no-site-packages" parameter to indicate that the virtual environment does not access global site-packages.

$ virtualenv --no-site-packages test2New python executable in test2/bin/pythonInstalling setuptools............done.$ cd test2test2$ source bin/activate(test2)test2$ python>>> import sys>>> sys.path['', '/home/yuhen/projects/python/test2/lib/python2.6/site-packages/setuptools-0.6c11-py2.6.egg','/home/yuhen/projects/python/test2/lib/python2.6/site-packages/pip-0.7.2-py2.6.egg', '/home/yuhen/projects/python/test2/lib/python2.6', '/home/yuhen/projects/python/test2/lib/python2.6/plat-linux2', '/home/yuhen/projects/python/test2/lib/python2.6/lib-tk', '/home/yuhen/projects/python/test2/lib/python2.6/lib-old', '/home/yuhen/projects/python/test2/lib/python2.6/lib-dynload', '/usr/lib/python2.6', '/usr/lib64/python2.6', '/usr/lib/python2.6/plat-linux2', '/usr/lib/python2.6/lib-tk', '/usr/lib64/python2.6/lib-tk', '/home/yuhen/projects/python/test2/lib/python2.6/site-packages']>>>

In the search path, except for the python basic library path, Global Site-packages is no longer available. In this way, even if we have installed a large number of development kits, we can isolate a clean test environment.

To determine whether a virtual environment is -- no-site-packages, in addition to checking SYS. path, you can also determine through the "lib/python2.6/no-global-site-packages.txt" file.