Failed to start the kernel on jupyter notebook

Question

I have python versions 3.6.5_1 and 3.7.0installed via Homebrew.
jupyter needs python3.6 for launching. It wouldn't start if I switch to python3.7.

After launching, it fails to start the kernel. Giving this error:

Traceback (most recent call last):
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/web.py", line 1543, in _execute
result = yield result
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 1099, in run
value = future.result()
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 1107, in run
yielded = self.gen.throw(*exc_info)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/notebook/services/sessions/handlers.py", line 73, in post
type=mtype))
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 1099, in run
value = future.result()
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 1107, in run
yielded = self.gen.throw(*exc_info)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/notebook/services/sessions/sessionmanager.py", line 79, in create_session
kernel_id = yield self.start_kernel_for_session(session_id, path, name, type, kernel_name)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 1099, in run
value = future.result()
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 1107, in run
yielded = self.gen.throw(*exc_info)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/notebook/services/sessions/sessionmanager.py", line 92, in start_kernel_for_session
self.kernel_manager.start_kernel(path=kernel_path, kernel_name=kernel_name)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 1099, in run
value = future.result()
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/vendor/lib/python3.6/site-packages/tornado/gen.py", line 315, in wrapper
yielded = next(result)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/notebook/services/kernels/kernelmanager.py", line 148, in start_kernel
super(MappingKernelManager, self).start_kernel(**kwargs)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/jupyter_client/multikernelmanager.py", line 110, in start_kernel
km.start_kernel(**kwargs)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/jupyter_client/manager.py", line 259, in start_kernel
**kw)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/jupyter_client/manager.py", line 204, in _launch_kernel
return launch_kernel(kernel_cmd, **kw)
File "/usr/local/Cellar/jupyter/1.0.0_4/libexec/lib/python3.6/site-packages/jupyter_client/launcher.py", line 128, in launch_kernel
proc = Popen(cmd, **kwargs)
File "/usr/local/Cellar/python/3.6.5_1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/subprocess.py", line 709, in __init__
restore_signals, start_new_session)
File "/usr/local/Cellar/python/3.6.5_1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/subprocess.py", line 1344, in _execute_child
raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: '/usr/local/opt/python/bin/python3.7': '/usr/local/opt/python/bin/python3.7'

From what I understand, the kernel is looking for python3.7. My kernel list has just python3

$jupyter kernelspec list  
Available kernels:  
python3    /usr/local/etc/jupyter/kernels/python3  

I looked at this link on github, but it wasn't helpful. How do I make jupyter and the kernel running on the same python version?

Answer 1

Check the kernel specifications:

$jupyter kernelspec list

This will show you the available kernels. In this case:

python3    /usr/local/etc/jupyter/kernels/python3  

Open the kernel.json file in this directory and specify the path of python you want the kernel to use in the argv key.

Answer 2

Updating the jupyter notebook resolved the issue for me. But remember, update it using command line. Not Anaconda Navigator

pip install -U jupyter

Answer 3

In case anyone anyone reading this who runs Jupyter Notebook from within Anaconda and gets the same error:

I found a workaround by installing Jupyter using pip in the command prompt (not anaconda prompt):

$pip install jupyter

and then start Jupyter using the known way

$cd 'DirectoryofyourNotebook'
$jupyter notebook