Python module cv2 is not available after "sudo apt-get install python-opencv"

I want to dabble with qr codes in Python.

pip3 install opencv-python fails on "skbuild". I read the FAQ here, but pip3 will not upgrade itself. That fails with a long list of red text.

From the FAQ:

Q: Pip install fails with ModuleNotFoundError: No module named 'skbuild'?

Since opencv-python version 4.3.0.*, manylinux1 wheels were replaced by manylinux2014 wheels. If your pip is too old, it will try to use the new source distribution introduced in 4.3.0.38 to manually build OpenCV because it does not know how to install manylinux2014 wheels. However, source build will also fail because of too old pip because it does not understand build dependencies in pyproject.toml. To use the new manylinux2014 pre-built wheels (or to build from source), your pip version must be >= 19.3. Please upgrade pip with pip install --upgrade pip.

I have this version of pip:

pedro@pedro-512ssd:~$ pip3 --version pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6) pedro@pedro-512ssd:~$

I saw on another webpage that I could get prebuilt binaries:

sudo apt-get install python-opencv

I did this, no errors, but the Python module cv2 is still not available. In Idle I see:

import cv2 Traceback (most recent call last): File "<pyshell#0>", line 1, in import cv2 ModuleNotFoundError: No module named 'cv2'

I rebooted, just in case that was necessary, but cv2 is still not available.

How can I get the Python module cv2 up and running??

Normally, I can get any module with a quick pip3 install the-Module-I-want.