A.6 The Python interpreter

The Python interpreter is a classic example of a command-line-driven Read-Evaluate-Print-Loop (REPL).

Figure A.1 shows how I start Python from the operating system command line.

Figure A.1: The Python interpreter

After displaying version information, Python displays a “>>>” prompt. I enter the first command: 2 + 3.

• Python reads 2 + 3 and parses it into an internal data structure it can manipulate.
• It then determines that it must evaluate the expression by applying “+” to int 2 and int 3. It does so and produces the result 5.
• Since the result is not None, Python prints 5.
• It then displays another “>>>” and waits for input.

The next expression is import math. Python reads and evaluates this code and loads the math...