On Jul 27, 2016, at 05:06 PM, Matijs van Zuijlen wrote: >virtualenv allows specifying the python version to use. However, when >doing so I get the following output: > > $ virtualenv -p /usr/bin/python3 --system-site-packages .venv > Already using interpreter /usr/bin/python3 > [..] > >It seems to indicate I didn't need to pass in the python interpreter to >use.
This message is telling you that the -p option is exactly the same path as sys.executable. Basically when virtualenv is invoked with a -p that isn't sys.executable, it will re-exec itself with the requested interpreter. However, in Debian, /usr/bin/virtualenv is shebanged to /usr/bin/python3 even though the default -p option is still /usr/bin/python. This is why you don't get this console message with the default invocation. Generally virtualenv's shebang is unimportant. I agree the warning is a little confusing, but I don't think it's worth changing in Debian. I'm not even sure it's worth reporting upstream. You can just safely ignore the message.