virtualenv without interfering #!/usr/bin/env python

Question

My application is writen in python 3, and I work in a virtualenv. On my cluster, there is hdp (hortonworks) installed and some scripts require python 2. Those script have #!/usr/bin/env python in the header, but it links to my python 3 installation because my virtualenv is activated. How to solve this ? I can't modify hdp source for obvious reasons.

Answer 1

Modifying Your Virtualenv

If you want your virtualenv to always be ignored with a #!/usr/bin/env python shebang (but not with a #!/usr/bin/env python3 shebang), there's a big-hammer approach that prevents the python entry in the PATH added by the virtualenv from matching, but doesn't necessarily perform other cleanup:

rm "$VIRTUAL_ENV/bin/python"

...or a better-behaved alternative (assuming that you have a python2.7 in your PATH, and that it's what you want to use):

cat >"$VIRTUAL_ENV/bin/python" <<'EOF'
#!/usr/bin/env bash
path_prefix=$VIRTUAL_ENV/bin:
if [[ $PATH = $path_prefix* ]]; then
  PATH=${PATH#$path_prefix}
fi

unset PYTHONHOME VIRTUAL_ENV
exec python2.7 "$@"
EOF

The below will assume you're looking for approaches with a bit more finesse .

---

Command-Specific Shell Wrapper

If you interact with Hortonworks through a frontend called hdp , consider the following a shell function, a wrapper for hdp that deactivates the virtualenv:

hdp() (
  if [[ $VIRTUAL_ENV ]]; then
    deactivate
  fi
  exec command hdp "$@"
)

Because this function is using parentheses instead of curly braces, it runs in a subshell -- a separate copy of the shell environment -- so when it runs deactivate , this doesn't impact your parent shell. This also means that the exec command causes the subshell to replace itself with the hdp command, rather than causing your parent shell to terminate.

---

Generic Shell Wrapper

If you want to be able to run other scripts with your virtualenv temporarily deactivated, consider instead:

# wv == "without virtualenv"
wv() (
  if [[ $VIRTUAL_ENV ]]; then
    deactivate
  fi
  exec "$@"
)

...such that wv foo will run foo with the virtualenv deactivated.