solved the problem by running sudo raspi-config, then "Advanced Options", then "GL Driver", "then select GL (Fake KMS)". I am using a Raspberry Pi 3 B+ with Raspberry Pi OS Buster.

As it says in the official documentation https://www.raspberrypi.com/documentati ... amera.html ….can be installed in Buster using sudo apt install libcamera-apps

Formatting The string format

1.7.1 Math functions

The len() function returns the length of a string:

Python has a set of built-in methods that you can use on lists/arrays

Float is a function or reusable code in the Python programming language that converts values into floating point numbers. Floating point numbers are decimal values or fractional numbers like 133.5, 2897.11, and 3571.213, whereas real numbers like 56, 2, and 33 are called integers.

Python dictionaries are another collection. Real word dictionaries are a good analogy to understand them: they contain a list of items, each item has a key and a value. In the traditional dictionary, the key is the word and the value is the explanation or description of it. In Python you can do something similar.

CamelCase is formally referred to as medial capitals. It may also be called or styled as PascalCase, camel case, InterCaps, mixedCase or WikiCase.

CamelCase is a way to separate the words in a phrase by making the first letter of each word capitalized and not using spaces

Integers

Note: Triple quotes, according to official Python documentation are docstrings, or multi-line docstrings and are not considered comments. Anything inside triple quotes is read by the interpreter. When the interpreter encounters the hash symbol, it ignores everything after that. That is what a comment is defined to be. 

Snake case (stylized as snake_case) refers to the style of writing in which each space is replaced by an underscore (_) character, and the first letter of each word written in lowercase. It is a commonly used naming convention in computing, for example for variable and subroutine names, and for filenames.

PascalCase