Programs can be quite complicated and are often thousands of lines long. It can be helpful to write a comment describing parts of the code so that when you or someone else reads it the meaning is clear.
In Python, any time the # character is encountered, Python will ignore the rest of the line. This allows you to write English sentences:
| >>> # Python ignores this sentence because of the # symbol. |
The # symbol does not have to be the first character on the line; it can appear at the end of a statement:
| >>> (212 - 32) * 5 / 9 # Convert 212 degrees Fahrenheit to Celsius. |
| 100.0 |
Notice that the comment doesn’t describe how Python works. Instead, it is meant for humans reading the code to help them understand why the code exists.