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Author Dieter Weber
Recipients Dieter Weber
Date 2019-01-10.14:04:59
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
Python virtual environments are awesome! Using venvs with an embedded Python interpreter has proven difficult, unfortunately. With conda environments it works. See appended a sample file to reproduce the behavior.

The core of the problem seems to be that a venv doesn't contain a full Python installation, and Py_Initialize() apparently doesn't support setting up the combination of venv directories and base installation correctly, i.e. setting sys.prefix and sys.base_prefix and potentially other values.

Observed behavior when trying to use a venv:

Initializing... Fatal Python error: Py_Initialize: unable to load the file system codec
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00001e90 (most recent call first):

Expected behavior:
Setting Py_SetPythonHome() to a venv works and sets up all paths and prefixes correctly to use the venv, just like it does for a conda environment.
Date User Action Args
2019-01-10 14:05:02Dieter Webersetrecipients: + Dieter Weber
2019-01-10 14:04:59Dieter Webersetmessageid: <>
2019-01-10 14:04:59Dieter Weberlinkissue35706 messages
2019-01-10 14:04:59Dieter Webercreate