Multiple Kernels in Python Jupyter Notebook

Question

I currently have Python 3 installed and want to install Python 2.7 as a second kernel in Jupyter notebook. I was able to install Python 2.7, however, when I change kernels in Jupyter notebook, I receive the following error in the Anaconda command prompt:

    [I 17:49:16.185 NotebookApp] Starting buffering for 069e4484-8d64-46e2-b62a-3588e46b4686:2857761af92f4e9387378c8162efbf40
[I 17:49:16.406 NotebookApp] Kernel shutdown: 069e4484-8d64-46e2-b62a-3588e46b4686
[I 17:49:16.453 NotebookApp] Kernel started: a9d7404d-02f1-4295-854d-0b11120cd3d2
Traceback (most recent call last):
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel_launcher.py", line 15, in <module>
    from ipykernel import kernelapp as app
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\__init__.py", line 2, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\connect.py", line 18, in <module>
    import jupyter_client
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\__init__.py", line 4, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\connect.py", line 24, in <module>
    import zmq
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\__init__.py", line 47, in <module>
    from zmq import backend
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 40, in <module>
    reraise(*exc_info)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 27, in <module>
    _ns = select_backend(first)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\select.py", line 28, in select_backend
    mod = __import__(name, fromlist=public_api)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\cython\__init__.py", line 6, in <module>
    from . import (constants, error, message, context,
ImportError: DLL load failed: The specified module could not be found.
[I 17:49:19.462 NotebookApp] KernelRestarter: restarting kernel (1/5), new random ports
Traceback (most recent call last):
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel_launcher.py", line 15, in <module>
    from ipykernel import kernelapp as app
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\__init__.py", line 2, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\connect.py", line 18, in <module>
    import jupyter_client
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\__init__.py", line 4, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\connect.py", line 24, in <module>
    import zmq
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\__init__.py", line 47, in <module>
    from zmq import backend
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 40, in <module>
    reraise(*exc_info)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 27, in <module>
    _ns = select_backend(first)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\select.py", line 28, in select_backend
    mod = __import__(name, fromlist=public_api)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\cython\__init__.py", line 6, in <module>
    from . import (constants, error, message, context,
ImportError: DLL load failed: The specified module could not be found.
[I 17:49:22.484 NotebookApp] KernelRestarter: restarting kernel (2/5), new random ports
Traceback (most recent call last):
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel_launcher.py", line 15, in <module>
    from ipykernel import kernelapp as app
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\__init__.py", line 2, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\connect.py", line 18, in <module>
    import jupyter_client
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\__init__.py", line 4, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\connect.py", line 24, in <module>
    import zmq
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\__init__.py", line 47, in <module>
    from zmq import backend
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 40, in <module>
    reraise(*exc_info)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 27, in <module>
    _ns = select_backend(first)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\select.py", line 28, in select_backend
    mod = __import__(name, fromlist=public_api)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\cython\__init__.py", line 6, in <module>
    from . import (constants, error, message, context,
ImportError: DLL load failed: The specified module could not be found.
[I 17:49:25.514 NotebookApp] KernelRestarter: restarting kernel (3/5), new random ports
Traceback (most recent call last):
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel_launcher.py", line 15, in <module>
    from ipykernel import kernelapp as app
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\__init__.py", line 2, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\connect.py", line 18, in <module>
    import jupyter_client
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\__init__.py", line 4, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\connect.py", line 24, in <module>
    import zmq
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\__init__.py", line 47, in <module>
    from zmq import backend
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 40, in <module>
    reraise(*exc_info)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 27, in <module>
    _ns = select_backend(first)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\select.py", line 28, in select_backend
    mod = __import__(name, fromlist=public_api)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\cython\__init__.py", line 6, in <module>
    from . import (constants, error, message, context,
ImportError: DLL load failed: The specified module could not be found.
[I 17:49:28.529 NotebookApp] KernelRestarter: restarting kernel (4/5), new random ports
Traceback (most recent call last):
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel_launcher.py", line 15, in <module>
    from ipykernel import kernelapp as app
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\__init__.py", line 2, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\ipykernel\connect.py", line 18, in <module>
    import jupyter_client
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\__init__.py", line 4, in <module>
    from .connect import *
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\jupyter_client\connect.py", line 24, in <module>
    import zmq
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\__init__.py", line 47, in <module>
    from zmq import backend
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 40, in <module>
    reraise(*exc_info)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\__init__.py", line 27, in <module>
    _ns = select_backend(first)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\select.py", line 28, in select_backend
    mod = __import__(name, fromlist=public_api)
  File "C:\Users\Nick Alexander\Anaconda3\envs\py27\lib\site-packages\zmq\backend\cython\__init__.py", line 6, in <module>
    from . import (constants, error, message, context,
ImportError: DLL load failed: The specified module could not be found.
[W 17:49:31.528 NotebookApp] KernelRestarter: restart failed
[W 17:49:31.528 NotebookApp] Kernel a9d7404d-02f1-4295-854d-0b11120cd3d2 died, removing from map.

All the python 2.7 installation files seem to be in the path specified by the error message. Thanks!

Answer 1

I'm not sure this solves your problem but try running

\path\to\your\install\of\python\python2.7 -m jupyter notebook

This will open jupyter in python2.7 hopefully

Answer 2

Do you have Anaconda installed?

With Anaconda you can easily create a new virtual environment with the desired python version:

conda create --name py27 python=2.7

will create a new environment with Python version 2.7.

conda create --name py37 python=3.7

will create a new environment with Python version 3.7.

This is the best way to use multiple Python releases on the same machine - in my opinion - furthermore you don't need to install any version of Python in your machine, Anaconda will do it for you.