#Class Notes

Virtualenvs (Demo)

Virtualenvs are isolated complete python environments,

• pip can be used to install python modules in them.
• are normally run as normal user
• no root priviledges are needed to install python modules in them.

Creating a virtualenv

[mike@localhost demo]$ virtualenv  -p python   testenv 
Already using interpreter /usr/bin/python
New python executable in testenv/bin/python
Installing Setuptools..............................................................................................................................................................................................................................done.
Installing Pip.....................................................................................................................................................................................................................................................................................................................................done.
[mike@localhost demo]$ ls
testenv
[mike@localhost demo]$ 

This virtualenv can be used by:

[mikef@localhost demo]$ source testenv/bin/activate
(testenv)[mikef@localhost demo]$ which python
~/demo/testenv/bin/python

The python in use is then not what is available system wide.

Installing python module packages with pip

(testenv)[mike@localhost demo]$ pip install psutil
Downloading/unpacking psutil
  Downloading psutil-2.1.3.tar.gz (224kB): 224kB downloaded
  Running setup.py egg_info for package psutil
    
    warning: no previously-included files matching '*' found under directory 'docs/_build'
Installing collected packages: psutil
  Running setup.py install for psutil
    building '_psutil_linux' extension
    gcc -pthread -fno-strict-aliasing -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/include/python2.7 -c psutil/_psutil_linux.c -o build/temp.linux-x86_64-2.7/psutil/_psutil_linux.o
    gcc -pthread -shared -Wl,-z,relro build/temp.linux-x86_64-2.7/psutil/_psutil_linux.o -L/usr/lib64 -lpython2.7 -o build/lib.linux-x86_64-2.7/_psutil_linux.so
    building '_psutil_posix' extension
    gcc -pthread -fno-strict-aliasing -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -DNDEBUG -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/include/python2.7 -c psutil/_psutil_posix.c -o build/temp.linux-x86_64-2.7/psutil/_psutil_posix.o
    gcc -pthread -shared -Wl,-z,relro build/temp.linux-x86_64-2.7/psutil/_psutil_posix.o -L/usr/lib64 -lpython2.7 -o build/lib.linux-x86_64-2.7/_psutil_posix.so
    
    warning: no previously-included files matching '*' found under directory 'docs/_build'
Successfully installed psutil
Cleaning up...
(testenv)[mike@localhost demo]$

the pip command will fetch the source from the cheese shop (pypi.python.org) compile it if neccesary and install it to the current virtualenv

Leaving the virtualenv

You can deactivate the virtualenv and use the system wide python via :

(testenv)[mike@localhost demo]$ deactivate
[mike@localhost demo]$ 

If you dont have virtualenv itself installed

You can get its source from pypi and use it thus:

[mike@localhost demo]$ wget https://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.11.6.tar.gz#md5=f61cdd983d2c4e6aeabb70b1060d6f49
--2014-11-17 10:08:57--  https://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.11.6.tar.gz
Resolving pypi.python.org (pypi.python.org)... 185.31.17.223
Connecting to pypi.python.org (pypi.python.org)|185.31.17.223|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1610581 (1.5M) [application/octet-stream]
Saving to: ‘virtualenv-1.11.6.tar.gz’

100%[=======================================================================================================================>] 1,610,581   4.65MB/s   in 0.3s   

2014-11-17 10:08:58 (4.65 MB/s) - ‘virtualenv-1.11.6.tar.gz’ saved [1610581/1610581]

[mike@localhost demo]$ tar -xf virtualenv-1.11.6.tar.gz 
[mike@localhost demo]$ ls virtualenv-1.11.6/
AUTHORS.txt  docs         MANIFEST.in  README.rst  setup.cfg  virtualenv.egg-info  virtualenv.py
bin          LICENSE.txt  PKG-INFO     scripts     setup.py   virtualenv_embedded  virtualenv_support
[mike@localhost demo]$ python virtualenv-1.11.6/virtualenv.py   -p python  newenv 
Already using interpreter /usr/bin/python
New python executable in newenv/bin/python
Installing setuptools, pip...done.
[mike@localhost demo]$ ls
newenv  testenv  virtualenv-1.11.6  virtualenv-1.11.6.tar.gz
[mike@localhost demo]$ source newenv/bin/activate
(newenv)[mike@localhost demo]$ deactivate
[mike@localhost demo]$

Instructions

Use the virtualenvs in the excercises, dont install python packages to the system-wide python location.