NUIT sometimes see University Ubuntu systems where the graphical desktop is missing because the colleague or student has attempted to remove the system Python, some of the system’s essential Python libraries and applications, or both. Other times, we see system applications not working properly because the colleague or student has installed a different Python version alongside the system Python and then set the new Python version to be the default
python3
command system-wide.
This damage leaves the system unusable, preventing the colleague or student from working. The only solution is for NUIT to reinstall the Ubuntu operating system.
What to avoid
~ $ pyenv install 3.12
Downloading Python-3.12.1.tar.xz...
-> https://www.python.org/ftp/python/3.12.1/Python-3.12.1.tar.xz
Installing Python-3.12.1...
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/home/campus.ncl.ac.uk/me/.pyenv/versions/3.12.1/lib/python3.12/bz2.py", line 17, in <module>
from _bz2 import BZ2Compressor, BZ2Decompressor
ModuleNotFoundError: No module named '_bz2'
WARNING: The Python bz2 extension was not compiled. Missing the bzip2 lib?
[many lines omitted]
Installed Python-3.12.1 to /home/campus.ncl.ac.uk/me/.pyenv/versions/3.12.1
You must infer these missing dependencies from the errors that
pyenv install 3.12
emits, so what you need may not match the packages listed below.
apt search
thing
and
yum search
thing
will be useful for this.
What I needed to install when writing this guide, to give an example of the kind of dependencies you might need:
On Ubuntu 24.04 systems, you also need to install
zlib1g-dev
otherwise you get the unhelpfully-opaque:
student@labC1QBRO:~$ pyenv install 3.12
Downloading Python-3.12.5.tar.xz...
-> https://www.python.org/ftp/python/3.12.5/Python-3.12.5.tar.xz
Installing Python-3.12.5...
BUILD FAILED (Ubuntu 24.04 using python-build 20180424)
Inspect or clean up the working tree at /tmp/python-build.20240903154016.7543
Results logged to /tmp/python-build.20240903154016.7543.log
Last 10 log lines:
File "/tmp/python-build.20240903154016.7543/Python-3.12.5/Lib/ensurepip/__init__.py", line 200, in _bootstrap
return _run_pip([*args, *_PACKAGE_NAMES], additional_paths)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/tmp/python-build.20240903154016.7543/Python-3.12.5/Lib/ensurepip/__init__.py", line 101, in _run_pip
return subprocess.run(cmd, check=True).returncode
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/tmp/python-build.20240903154016.7543/Python-3.12.5/Lib/subprocess.py", line 571, in run
raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['/tmp/python-build.20240903154016.7543/Python-3.12.5/python', '-W', 'ignore::DeprecationWarning', '-c', '\nimport runpy\nimport sys\nsys.path = [\'/tmp/tmpjoslp4b2/pip-24.2-py3-none-any.whl\'] + sys.path\nsys.argv[1:] = [\'install\', \'--no-cache-dir\', \'--no-index\', \'--find-links\', \'/tmp/tmpjoslp4b2\', \'--root\', \'/\', \'--upgrade\', \'pip\']\nrunpy.run_module("pip", run_name="__main__", alter_sys=True)\n']' returned non-zero exit status 1.
make: *** [Makefile:2027: install] Error 1
Set up the aliases
Pyenv gives you a Python interpreter that answers to the name
python
. To have it also answer to
python3
and switch between the system Python and Pyenv-installed Pythons reliably, run:
sudo apt install python-is-python3
alias python3=python
Then add that alias to your shell’s run control file. The wide variety of shells in use means that we cannot give specific instructions for that.
If you don’t install python-is-python3 and don’t set up the alias, you see outcomes like:
~ $ pyenv local 3.12.1
~ $ python --version
Python 3.12.1
~ $ python3 --version
Python 3.10.12
~ $ pyenv local system
~ $ python --version
pyenv: python: command not found
The `python' command exists in these Python versions:
3.12.1
Pyenv demonstration
The below demonstrates how Pyenv can be used to set up a directory for a project that needs a specific Python version without affecting the Python version used elsewhere:
