Why is there no python command?

Problem

I have a Python script with this shebang:

#! /usr/bin/env python

However, when I run it, I get this error:

/usr/bin/env: 'python': No such file or directory

How come? This used to work!

Reason

From Debian 11 (bullseye) and its derivatives, like ubuntu 20.04 LTS, none of the package Python scripts use #! /usr/bin/python, but either #! /usr/bin/python2 or #! /usr/bin/python3. Thus, neither the python2 package nor the python3 package create such a binary or symlink.

Solution

You can either create the symlink yourself:

# ln -s /usr/bin/python3 /usr/bin/python

or install a package that creates the symlink for you:

# apt-get install python-is-python3

Note, in Debian 11 and Ubuntu 20.04 there was also a python-is-python2, but this will be removed in the upcoming Debian 12 (bookworm) and thus in Ubuntu 22.04 LTS.

Closing remarks

You should really change your shebangs to use python2 or python3 since there are significant differences between the two. And of course, if you are still using python2, you should consider migrating to python3, the command 2to3 will give you a good starting point.

Happy coding!