Learning Python, 5th Edition

Chapter 10. Introducing Python Statements

Now that you’re familiar with Python’s core built-in object types, this chapter begins our exploration of its fundamental statement forms. As in the previous part, we’ll begin here with a general introduction to statement syntax, and we’ll follow up with more details about specific statements in the next few chapters.

In simple terms, statements are the things you write to tell Python what your programs should do. If, as suggested in Chapter 4, programs “do things with stuff,” then statements are the way you specify what sort of things a program does. Less informally, Python is a procedural, statement-based language; by combining statements, you specify a procedure that Python performs to satisfy a program’s goals.

The Python Conceptual Hierarchy Revisited

Another way to understand the role of statements is to revisit the concept hierarchy introduced in Chapter 4, which talked about built-in objects and the expressions used to manipulate them. This chapter climbs the hierarchy to the next level of Python program structure:

1. Programs are composed of modules.

2. Modules contain statements.

3. Statements contain expressions.

4. Expressions create and process objects.

At their base, programs written in the Python language are composed of statements and expressions. Expressions process objects and are embedded in statements. Statements code the larger logic of a program’s operation—they use and direct expressions to process the objects we studied in the preceding ...