Introducing Python

Chapter 4. Py Crust: Code Structures

In Chapters 1 through 3, you’ve seen many examples of data but have not done much with them. Most of the code examples used the interactive interpreter and were short. Now you’ll see how to structure Python code, not just data.

Many computer languages use characters such as curly braces ({ and }) or keywords such as begin and end to mark off sections of code. In those languages, it’s good practice to use consistent indentation to make your program more readable for yourself and others. There are even tools to make your code line up nicely.

When he was designing the language that became Python, Guido van Rossum decided that the indentation itself was enough to define a program’s structure, and avoided typing all those parentheses and curly braces. Python is unusual in this use of white space to define program structure. It’s one of the first aspects that newcomers notice, and it can seem odd to those who have experience with other languages. It turns out that after writing Python for a little while, it feels natural and you stop noticing it. You even get used to doing more while typing less.

Comment with #

A comment is a piece of text in your program that is ignored by the Python interpreter. You might use comments to clarify nearby Python code, make notes to yourself to fix something someday, or for whatever purpose you like. You mark a comment by using the # character; everything from that point on to the end of the current line is part of ...