This goes in a `settings` package, imported from settings modules with `from .base_dirs import PROJECT_DIR, VAR_ROOT`

base_dirs.py

"""
Calculates some project directory settings by assuming they are relative this
module's location.

``PROJECT_DIR``
    The project module's path.

``VAR_ROOT``
    A location to put run-time generated files (such as uploaded files, or the
    collation of static files).

    If running in a virtual environment, this will be ``$VIRTUAL_ENV/var``,
    otherwise it will be ``$PROJECT_DIR/local``.
"""
import os
import sys

PROJECT_DIR = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))

python_bin_dir = os.path.dirname(sys.executable)
# Assume that the presence of 'activate_this.py' in the python bin/ directory
# means that we're running in a virtual environment.
if os.path.exists(os.path.join(python_bin_dir, 'activate_this.py')):
    # We're running with a virtualenv python executable.
    VAR_ROOT = os.path.join(os.path.dirname(python_bin_dir), 'var')
else:
    venv_dir = os.path.dirname(os.path.dirname(os.path.dirname(PROJECT_DIR)))
    if venv_dir and os.path.exists(
            os.path.join(venv_dir, 'bin', 'activate_this.py')):
        # We're running in [virtualenv_root]/src/[project_name].
        VAR_ROOT = os.path.join(venv_dir, 'var')
    else:
        # Set the variable root to the local configuration location (which is
        # ignored by the repository).
        VAR_ROOT = os.path.join(PROJECT_DIR, 'local', 'var')

if not os.path.exists(VAR_ROOT):
    os.mkdir(VAR_ROOT)