# 43.10\. Environment Variables Some of the environment variables that are accepted by the Python interpreter can also be used to affect PL/Python behavior. They would need to be set in the environment of the main PostgreSQL server process, for example in a start script. The available environment variables depend on the version of Python; see the Python documentation for details. At the time of this writing, the following environment variables have an affect on PL/Python, assuming an adequate Python version: * `PYTHONHOME` * `PYTHONPATH` * `PYTHONY2K` * `PYTHONOPTIMIZE` * `PYTHONDEBUG` * `PYTHONVERBOSE` * `PYTHONCASEOK` * `PYTHONDONTWRITEBYTECODE` * `PYTHONIOENCODING` * `PYTHONUSERBASE` * `PYTHONHASHSEED` (It appears to be a Python implementation detail beyond the control of PL/Python that some of the environment variables listed on the `python` man page are only effective in a command-line interpreter and not an embedded Python interpreter.)