As programs get bigger and more complicated, they get more difficult to read. Formal languages are dense, and it is often difficult to look at a piece of code and figure out what it is doing, or why. For this reason, it is a good idea to add notes to your programs to explain in natural language what the program is doing. These notes are called comments.

A comment in a computer program is text that is intended only for the human reader – it is completely ignored by the interpreter. In Python, the # token starts a comment. The rest of the line is ignored.