Calling IPython from a virtualenv

Question

I understand that IPython is not virtualenv-aware and that the most logical solution to this is to install ipython in each virtualenv seperately using

pip install ipython

So far so good. One thing I noticed is that if the system-wide copy of IPython is called from within a virtualenv using $> ipython before IPython is installed under this virtualenv, subsequent $> ipython commands will continue to bring up the system-wide ipython copy.

On the other hand, if ipython is not called prior to installing it under a virtualenv $> ipython will bring up the newly installed copy.

What is the explanation for this?

It also makes me wonder if this behavior means I should expect some trouble down the way?

Answer 1

alias ipy="python -c 'import IPython; IPython.terminal.ipapp.launch_new_instance()'"

This is a great way of always being sure that the ipython instance always belongs to the virtualenv's python version.

This works only on ipython >2.0.

Source

Answer 2

The answer given by @SiddharthaRT is good! Following this approach, it is simpler for me just:

python -m IPython

This will use the module IPython through the python bin, ensuring that it refers to the bin from the virtual env.

Answer 3

1. Activate your virtual environment by using source ~/.virtualenvs/my_venv/bin/activate or by running workon my_venv (Depending on how you've installed the my_venv virtual environment)

2. Install ipython

pip install ipython

3. Now run ipython from my_venv.

If it still loads the system's ipython, then run hash -r in your shell

This will reset the cache of your shell and ensure you don't run another ipython that was already called in this shell session.

Answer 4

You can force IPython to use a virtual environment if available by adding file below to ~/.ipython/profile_default/startups:

import os
import sys

if 'VIRTUAL_ENV' in os.environ:
    py_version = sys.version_info[:2] # formatted as X.Y 
    py_infix = os.path.join('lib', ('python%d.%d' % py_version))
    virtual_site = os.path.join(os.environ.get('VIRTUAL_ENV'), py_infix, 'site-packages')
    dist_site = os.path.join('/usr', py_infix, 'dist-packages')

    # OPTIONAL: exclude debian-based system distributions sites
    sys.path = filter(lambda p: not p.startswith(dist_site), sys.path)

    # add virtualenv site
    sys.path.insert(0, virtual_site)

I recommend naming it 00-virtualenv.py so changes will be made as early as possible.

Note: Make sure ipython is installed in the new virtual environment to get this to work.

Answer 5

As others mentioned, recent versions of ipython are virtualenv aware, so you can use your virtualenv bin activate script to run ipython using your virtualenv, e.g.

$ source venv/bin/activate
(venv) $ ipython
WARNING: Attempting to work in a virtualenv. If you encounter problems, please install IPython inside the virtualenv.

Answer 6

I'll chime in years later in hopes someone finds this useful.

This solution solves a few problems:

• You don't need iPython installed in the current virtualenv, only for the global Python that matches your virtualenv's Python version (3.6 != 3.7).
• Works for users of pyenv where your global Python version might be 3.7 and your local virtualenv Python is 3.6 therefore using the global ipython will fail.
• Works outside of virtual environments (though not particularly useful as it always targets python).

Throw this in your ~/.bashrc or ~/.zshrc or what have you:

# This is a roundabout way to start ipython from inside a virtualenv without it being installed
# in that virtualenv. The only caveot is that the "global" python must have ipython installed.
# What this function does that's different than simply calling the global ipython is it ensures to
# call the ipython that is installed for the same major.minor python version as in the virtualenv.
# This is most useful if you use pyenv for example as global python3 could be 3.7 and local
# virtualenv python3 is 3.6.
function ipy {
  local PY_BIN
  local IPYTHON
  local PYV
  # This quick way will work if ipython is in the virtualenv
  PY_BIN="$(python -c 'import sys; print(sys.executable)')"
  IPYTHON="$(dirname "$PY_BIN")/ipython"
  if [[ -x "$IPYTHON" ]]; then
    "$IPYTHON"
  else
    # Ask the current python what version it is
    PYV="$(python -c 'import sys; print(".".join(str(i) for i in sys.version_info[:2]))')"
    echo "Looking for iPython for Python $PYV"
    # In a new shell (where pyenv should load if equipped) try to find that version
    PY_BIN="$($SHELL -i -c "python$PYV -c 'import sys; print(sys.executable)'")"
    "$(dirname "$PY_BIN")/ipython"
  fi
}

Then source or open a new terminal and run ipy.

Answer 7

If you're trying to open a notebook, even ipython 5 won't help - ipython will disregard the virtualenv (at least on my machine/setup). You'll need to use rgtk's script, but please make sure to modify the optional filter part and the sys.path.insert as below:

import os
import sys

if 'VIRTUAL_ENV' in os.environ:
    py_version = sys.version_info[:2] # formatted as X.Y 
    py_infix = os.path.join('lib', ('python%d.%d' % py_version))
    virtual_site = os.path.join(os.environ.get('VIRTUAL_ENV'), py_infix, 'site-packages')
    dist_site = os.path.join('/usr', py_infix, 'dist-packages')

    # OPTIONAL: exclude debian-based system distributions sites
    # ADD1: sys.path must be a list
    sys.path = list(filter(lambda p: not p.startswith(dist_site), sys.path))

    # add virtualenv site
    # ADD2: insert(0 is wrong and breaks conformance of sys.path
    sys.path.insert(1, virtual_site)

• ADD1: in the original script we get back a filter object, we would break sys.path and insert below would fail
• ADD2: see this question and python documentation

Answer 8

(Debian/Ubuntu) assuming some version (x) of Python3 is installed, then:

$ sudo apt-get install -y ipython
$ virtualenv --python=python3.x .venv
$ source .venv/bin/activate
$ pip3 install ipython
$ ipython3

will launch ipython running your version of Python3.