Detect Python virtual environments venv and virtualenv

environment.py

def is_virtual():
    """ Return if we run in a virtual environtment. """
    # Check supports venv && virtualenv
    return (getattr(sys, 'base_prefix', sys.prefix) != sys.prefix or
            hasattr(sys, 'real_prefix'))

Hm, not sure this would work with https://www.continuum.io/anaconda-overview :/

from a shell script,

python -c "import sys; sys.exit(getattr(sys, 'base_prefix', sys.prefix) == sys.prefix)"

and check for $? value. It'll be 0 for being inside a virtualenv

EDIT: tested with python3.6.