ipykernel

7.2.0 · active · verified Sat Mar 28

ipykernel provides the IPython kernel, which serves as the Python execution backend for Jupyter Notebooks, JupyterLab, and other Jupyter frontends. It facilitates interactive Python development, supports rich media outputs, and enables seamless code sharing within these environments. The current stable version is 7.2.0, and the project maintains an active development and release cadence.

Warnings

breaking ipykernel 7.0.0 introduced significant architectural changes for kernel subshells, including handling shell channel messages in a separate thread. While intended to be backward compatible for non-subshell users, these changes may break assumptions made by downstream libraries. Users encountering issues should consider pinning to `ipykernel < 7`.
Fix: If issues arise, downgrade to `ipykernel < 7`. Review your code for assumptions about thread-local state or message timing. Consult the official changelog and GitHub issues for detailed migration guidance.
breaking Support for Python 3.9 was dropped in `ipykernel 7.0.0a3`. Users on Python 3.9 or older must use `ipykernel` version 6.x or earlier.
Fix: Upgrade your Python environment to 3.10 or newer, or pin `ipykernel < 7.0.0a3` (e.g., `pip install 'ipykernel<7'`).
gotcha Version 6.30.0 contained a bug that allowed control messages to be handled concurrently, which severely broke debugging in JupyterLab and VSCode. This was a critical regression fixed in version 6.30.1.
Fix: Ensure you are running `ipykernel` 6.30.1 or later if you were affected by this bug.
gotcha Prior to 7.1.0 (and 6.31.0 for the 6.x series), display outputs from magics like `%notebook` were not always included when saving sessions to `.ipynb` files, as `ZMQDisplayPublisher.store_display_history` defaulted to `False`.
Fix: Upgrade to `ipykernel 7.1.0` or `6.31.0` (or newer). If using an older version, you may need to manually configure `ZMQDisplayPublisher.store_display_history` if exposed.

Install

pip install ipykernel Install ipykernel
python -m ipykernel install --user --name=myenv --display-name="Python (My Environment)" Register kernel for Jupyter (recommended in a virtual environment)

Imports

embed_kernel
```
from ipykernel.embed import embed_kernel
```
Used for embedding an IPython kernel into a Python application, not typically for general Jupyter usage.

Quickstart

The primary use case for ipykernel is to provide a Python execution environment for Jupyter frontends. This quickstart demonstrates how to install ipykernel and register it as a new kernel in your current Python environment, making it available in Jupyter Notebook or JupyterLab. It's best practice to perform this within an activated virtual environment.

import subprocess
import sys
import os

# Ensure ipykernel is installed in the current environment
subprocess.check_call([sys.executable, '-m', 'pip', 'install', 'ipykernel'])

# Define a unique name for your kernel (e.g., based on virtual environment name)
env_name = os.environ.get('VIRTUAL_ENV', 'default_env').split(os.sep)[-1]
display_name = f"Python ({env_name.replace('_', ' ').title()} Environment)"

# Register the kernel with Jupyter
try:
    subprocess.check_call([
        sys.executable, '-m', 'ipykernel', 'install',
        '--user', f'--name={env_name}', f'--display-name={display_name}'
    ])
    print(f'Successfully registered Jupyter kernel: "{display_name}" (name: {env_name})')
    print('To use it, launch Jupyter Notebook/Lab and select this kernel for a new notebook.')
    print('You can verify installed kernels with: jupyter kernelspec list')
except subprocess.CalledProcessError as e:
    print(f'Failed to register kernel: {e}')
    print('Ensure Jupyter is installed (pip install notebook or pip install jupyterlab).')

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