We can have both Python 2 and Python 3 installed on any Windows or Linux device. We can either create different environments on different IDEs to use the versions separately or use the following ways to run them using the command prompt.
Using ipyparallelTo run code in parallel across cores on one node, you can start up with workers and run your parallel code all within your notebook, as described here. If you'd like to run workers in parallel across multiple nodes, this may be possible and feel free to contact us to discuss further.
The idea here is to install multiple ipython
kernels. Here are instructions for anaconda. If you are not using anaconda, I recently added instructions using pure virtualenvs.
Since version 4.1.0, anaconda includes a special package nb_conda_kernels
that detects conda environments with notebook kernels and automatically registers them. This makes using a new python version as easy as creating new conda environments:
conda create -n py27 python=2.7 ipykernel
conda create -n py36 python=3.6 ipykernel
After a restart of jupyter notebook, the new kernels are available over the graphical interface. Please note that new packages have to be explicitly installed into the new environments. The Managing environments section in conda's docs provides further information.
Users who do not want to use nb_conda_kernels
or still use older versions of anaconda can use the following steps to manually register ipython kernels.
configure the python2.7
environment:
conda create -n py27 python=2.7
conda activate py27
conda install notebook ipykernel
ipython kernel install --user
configure the python3.6
environment:
conda create -n py36 python=3.6
conda activate py36
conda install notebook ipykernel
ipython kernel install --user
After that you should be able to choose between python2
and python3
when creating a new notebook in the interface.
Additionally you can pass the --name
and --display-name
options to ipython kernel install
if you want to change the names of your kernels. See ipython kernel install --help
for more informations.
If you’re running Jupyter on Python 3, you can set up a Python 2 kernel like this:
python2 -m pip install ipykernel
python2 -m ipykernel install --user
http://ipython.readthedocs.io/en/stable/install/kernel_install.html
These instructions explain how to install a python2 and python3 kernel in separate virtual environments for non-anaconda users. If you are using anaconda, please find my other answer for a solution directly tailored to anaconda.
I assume that you already have jupyter notebook
installed.
First make sure that you have a python2
and a python3
interpreter with pip
available.
On ubuntu you would install these by:
sudo apt-get install python-dev python3-dev python-pip python3-pip
Next prepare and register the kernel environments
python -m pip install virtualenv --user
# configure python2 kernel
python -m virtualenv -p python2 ~/py2_kernel
source ~/py2_kernel/bin/activate
python -m pip install ipykernel
ipython kernel install --name py2 --user
deactivate
# configure python3 kernel
python -m virtualenv -p python3 ~/py3_kernel
source ~/py3_kernel/bin/activate
python -m pip install ipykernel
ipython kernel install --name py3 --user
deactivate
To make things easier, you may want to add shell aliases for the activation command to your shell config file. Depending on the system and shell you use, this can be e.g. ~/.bashrc
, ~/.bash_profile
or ~/.zshrc
alias kernel2='source ~/py2_kernel/bin/activate'
alias kernel3='source ~/py3_kernel/bin/activate'
After restarting your shell, you can now install new packages after activating the environment you want to use.
kernel2
python -m pip install <pkg-name>
deactivate
or
kernel3
python -m pip install <pkg-name>
deactivate
With a current version of the Notebook/Jupyter, you can create a Python3 kernel. After starting a new notebook application from the command line with Python 2 you should see an entry „Python 3“ in the dropdown menu „New“. This gives you a notebook that uses Python 3. So you can have two notebooks side-by-side with different Python versions.
mkdir -p ~/.ipython/kernels/python3
Create this file ~/.ipython/kernels/python3/kernel.json
with this content:
{
"display_name": "IPython (Python 3)",
"language": "python",
"argv": [
"python3",
"-c", "from IPython.kernel.zmq.kernelapp import main; main()",
"-f", "{connection_file}"
],
"codemirror_mode": {
"version": 2,
"name": "ipython"
}
}
Restart the notebook server.
A solution is available that allows me to keep my MacPorts installation by configuring the Ipython kernelspec.
Requirements:
For python 2.x:
$ cd /opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin
$ sudo ./ipython kernelspec install-self
For python 3.x:
$ cd /opt/local/Library/Frameworks/Python.framework/Versions/3.4/bin
$ sudo ./ipython kernelspec install-self
Now you can open an Ipython notebook and then choose a python 2.x or a python 3.x notebook.
From my Linux installation I did:
sudo ipython2 kernelspec install-self
And now my python 2 is back on the list.
Reference:
http://ipython.readthedocs.org/en/latest/install/kernel_install.html
UPDATE:
The method above is now deprecated and will be dropped in the future. The new method should be:
sudo ipython2 kernel install
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