run-python.el

(defun python-find-python-command (&optional root)
  "Return the python interpreter to use for ROOT."
  (let ((env-root (local-path
                   (locate-dominating-file
                    (or root default-directory) "bin/python"))))
    (or (when env-root (concat env-root "bin/python"))
        python-python-command)))

(defun python-find-project-root (&optional start)
  "Return the root of this Python project."
  (let ((start (or start default-directory)))
    (or (locate-dominating-file start "setup.py")
        (locate-dominating-file start ".git"))))

(defmacro with-virtualenv-python (&rest body)
  "Locate a local Python interpreter and make it available in the body."
  `(let* ((local-python-command (python-find-python-command))
          (python-command local-python-command)
          (python-python-command local-python-command)
          (test-case-python-executable local-python-command))
     ,@body))

(defun run-virtualenv-python (new)
  (interactive "P")
  (with-virtualenv-python
   (let ((default-directory (python-find-project-root)))
     (run-python python-python-command nil new))))