Python编程基础：从指令到交互与实践

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"《Python编程基础》是Rick Halterman撰写的一本教材，它深入探讨了计算机程序设计的基本原理和使用Python语言进行编程的方法。在书中，作者从软件开发的宏观视角出发，强调了程序作为一系列指令，如何通过控制计算机内部电路的电信号流动，实现对内存的操作、与输入设备如屏幕、键盘和网络交互，从而帮助人们完成各种任务，包括计算金融数据和进行游戏对战。章节1介绍了编程的背景，讨论了软件的概念、开发工具的选择以及学习编程，特别是使用Python的动机。通过编写简单的Python程序，读者能够理解程序执行的基本流程，以及Python交互式shell的作用，这是一个实时测试和调试代码的重要环境。在第2章中，核心概念如数值类型（整数、浮点数）和变量被深入解析。讲解了如何声明和赋值变量，以及标识符的使用规则。控制代码嵌入字符串中、用户输入的处理以及打印功能的控制都得到了详细的介绍。此外，字符串格式化和多行字符串的处理也是这一部分的重点。第三章转向表达式和算术运算，包括不同类型的表达式及其组合，解释了运算符的优先级和结合性，这对于正确理解和编写复杂的计算逻辑至关重要。同时，书中还涉及了注释的使用，这对于代码的可读性和维护性非常重要。《Fundamentals of Python Programming》旨在为初学者提供一个坚实的基础，使他们掌握基本的编程概念和语法，并通过实践练习提升技能。通过阅读和跟随书中的例子，读者将逐步学会如何用Python构建实用的程序，从而进入更高级别的问题解决和软件开发领域。这本书不仅适合大学入门课程，也适合自学者和希望深化Python基础的开发者阅读。"

1.4. WRITING A PYTHON PROGRAM 5

Python is used for software development at companies and organizations such as Google, Yahoo, Face-

book, CERN, Industrial Light and Magic, and NASA. Experienced programmers can accomplish great

things with Python, but Python’s beauty is that it is accessible to beginning programmers and allows them

to tackle interesting problems more quickly than many other, more complex languages that have a steeper

learning curve.

More information about Python, including links to download the latest version for Microsoft Windows,

Mac OS X, and Linux, can be found at http://www.python.org.

In late 2008, Python 3.0 was released. Commonly called Python 3, the current version of Python is

incompatible with earlier versions of the language. Currently the Python world still is in transition between

Python 2 and Python 3. Many existing published books cover Python 2, but more Python 3 resources now

are becoming widely available. The code in this book is based on Python 3.

This book does not attempt to cover all the facets of the Python programming language. Experienced

programmers should look elsewhere for books that cover Python in much more detail. The focus here is on

introducing programming techniques and developing good habits. To that end, our approach avoids some

of the more esoteric features of Python and concentrates on the programming basics that transfer directly to

other imperative programming languages such as Java, C#, and C

. We stick with the basics and explore

more advanced features of Python only when necessary to handle the problem at hand.

1.4 Writing a Python Program

The text that makes up a Python program has a particular structure. The syntax must be correct, or the

interpreter will generate error messages and not execute the program. This section introduces Python by

providing a simple example program.

A program consists of one or more statements. A statement is an instruction that the interpreter executes.

The following statement invokes the print function to display a message:

print("This is a simple Python program")

We can use the statement in a program. Listing 1.1 (simple.py) is one of the simplest Python programs that

does something:

Listing 1.1: simple.py

print("This is a simple Python program")

We will use Wingware’s WingIDE 101 to develop our Python programs. This integrated development

environment is freely available from http://wingware.com/downloads/wingide-101, and its target au-

dience is beginning Python programmers. Its feature set and ease of use make WingIDE 101 an ideal

platform for exploring programming in Python.

The way you launch WingIDE 101 depends on your operating system and how it was installed. Fig-

ure 1.1 shows a screenshot of WingIDE 101 running on a Windows 8.1 computer. The IDE consists of a

menu bar at the top, along with a tool bar directly underneath it, and several sub-panes within the window.

The large, unlabeled pane in the upper left portion of the window is the editor pane in which we type in

our program’s source code. The versions of WingIDE 101 for Apple Mac OS X and Linux are similar in

appearance.

To begin entering our program, we will choose the New item from the File menu (File→New menu

sequence), as shown in Figure 1.2. This action produces a new editor pane for a ﬁle named Unititled-1.py.

1.5. THE PYTHON INTERACTIVE SHELL 9

Figure 1.11 WingIDE 101 running under Microsoft Windows

we prefer the Debug option to the Run option.

When you are ﬁnished programming and wish to quit the IDE, follow the menu sequence File→Quit as

shown in Figure 1.11.

Listing 1.1 (simple.py) contains only one line of code:

print("This is a simple Python program")

This is a Python statement. A statement is a command that the interpreter executes. This statement

prints the message This is a simple Python program on the screen. A statement is the fundamental unit of

execution in a Python program. Statements may be grouped into larger chunks called blocks, and blocks can

make up more complex statements. Higher-order constructs such as functions and methods are composed

of blocks. The statement

print("This is a simple Python program")

makes use of a built in function named print. Python has a variety of different kinds of statements that we

can use to build programs, and the chapters that follow explore these various kinds of statements.

While integrated development environments like Wingware’s WingIDE-101 are useful for developing

Python programs, we can execute Python programs directly from a command line. In Microsoft Windows,

the command console (cmd.exe) and PowerShell offer command lines. In Apple Mac OS X, Linux, and

Unix, a terminal provides a command line. Figure 1.12 shows the Windows command shell running a

Python program. In all cases the user’s PATH environment variable must be set properly in order for the

operating system to ﬁnd the Python interpreter to run the program.

Figure 1.8 shows that WingIDE 101 displays a program’s output as black text on a white background. In

order to better distinguish visually in this text program source code from program output, we will render the

program’s output with white text on a black background, as it would appear in the command line interpreter

under Windows as shown in Figure 1.12. This means we would show the output of Listing 1.1 (simple.py)

This is a simple Python program

1.5 The Python Interactive Shell

We created the program in Listing 1.1 (simple.py) and submitted it to the Python interpreter for execution.

We can interact with the interpreter directly, typing in Python statements and expressions for its immediate

execution. As we saw in Figure 1.8, the WingIDE 101 pane labeled Python Shell is where the executing

program directs its output. We also can type commands into the Python Shell pane, and the interpreter

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