Setuptools
Entrypoints
Entrypoints are a way to specify components in your package to the rest of the python space, so they can be dynamically discovered. So this enables:
- Console scripts (command line tools): executable commands.
setuptoolsgenerates binaries in your Python environment’sbin, so they can be run. - Plugins
- Custom Extensions
Example setup.py:
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from setuptools import setup, find_packages
setup(
name='your_package_name',
version='0.0.1',
packages=find_packages(),
install_requires=['setuptools'],
entry_points={
'console_scripts': [
'your_command = your_package.module:function',
],
# Other entry point groups can be defined here
},
)
- In ROS2, the most commonly used entrypoints are console scripts.
Pip
Externally Managed Environment
When you see “externally managed environment,” it means your system’s Python installation is controlled by your OS’s package manager (e.g. Debian’s apt), not by pip. To keep the system stable, Debian (and other distros) disable pip’s ability to write into the global site-packages directory. That way, all core Python libraries stay under apt’s control and can’t be accidentally broken by a pip upgrade.
- “Core Python libraries” are the modules that ship as part of your Python installation
- System Python
.debpackages:python3-stdlib,python3-distutils,python3-venv, etc.
- System Python
PEP 668 formalizes this: an “externally managed” Python cannot be modified by user-level pip installs.
- What is a “core python library”? Does this mean i can’t use pip?
So, one can install using apt: sudo apt install python3-ipykernel
