python - completely self-contained virtual environment -

i create python3 virtual environment (explicitly avoiding symlinks, --copies):

» python3 -m venv --without-pip --copies venv 

this complete virtual environment now:

» tree venv/ venv/ ├── bin │   ├── activate │   ├── activate.csh │   ├── activate.fish │   ├── python │   └── python3 ├── include ├── lib │   └── python3.4 │       └── site-packages ├── lib64 -> lib └── pyvenv.cfg 

i disable pythonpath, make sure nothing leaking outside:

» pythonpath="" 

activate venv:

» source venv/bin/activate 

verify activate has not polluted pythonpath:

» echo $pythonpath 

(blank, expected)

i using right python:

» python /foo/bar/venv/bin/python 

but system modules still being accessed:

» python  python 3.4.3 (default, oct 14 2015, 20:28:29)  [gcc 4.8.4] on linux type "help", "copyright", "credits" or "license" more information. >>> import unittest >>> print(unittest) <module 'unittest' '/usr/lib/python3.4/unittest/__init__.py'> >>>  

i expect import unittest statement fail, since virtual environment has no such module.

i know:

• why system packages accessed when in virtualenv?
• how can create self-contained virtual environment?

if recall correctly core system packages symlinked, same files (partly keep size of virtualenv down).

the default not include site-packages directory, won't access 3rd party libraries have been installed.

if want isolated , self-contained virtual environment, might better off looking @ docker.

virtualenv more of lightweight way of managing different 3rd party installed packages different apps.

edit:

it looks --always-copy doesn't copy files:

virtualenv doesn't copy .py files lib/python directory

digging source , looks there's smallish set of modules deemed "required" , these ones copied:

https://github.com/pypa/virtualenv/blob/ac4ea65b14270caeac56b1e1e64c56928037ebe2/virtualenv.py#l116

edit 2:

you can see old python directories still appear in sys.path, after directories virtualenv itself:

>>> import sys >>> sys.path ['', '/home/john/venv/lib/python2.7',  '/home/john/venv/lib/python2.7/plat-linux2',  '/home/john/venv/lib/python2.7/lib-tk', '/home/john/venv/lib/python2.7/lib-old',  '/home/john/venv/lib/python2.7/lib-dynload', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/home/john/venv/local/lib/python2.7/site-packages', '/home/john/venv/lib/python2.7/site-packages']