# 45.11. 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.)


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