Calling IPython from a virtualenv

问题:

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?

回答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

回答2:

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.

回答3:

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.

回答4:

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.

回答5:

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

回答6:

(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.