[Dark Horse] net course notes first Python program

First Python Program

aims

• The first HelloPythonprogram
• Python 2.xAnd 3​​.xversion Introduction
• The implementation of Pythonthree ways to program
  • Interpreter - python/python3
  • Interactive - ipython
  • Integrated Development Environment-- PyCharm

01. The first HelloPythonprogram

Basic Concepts 1.1 Python source code

1. Python source code is a text file of a special format , you can use any text editor to do Pythondevelopment
2. Python program file extensions are usually.py

Step drills 1.2

• In the desktop, create a new 认识Pythondirectory
• In 认识Pythonthe new directory 01-HelloPython.pyfile
• Use gedit editor 01-HelloPython.pyand enter the following:

print("hello python")
print("hello world")

• Enter the following command in the terminal execution 01-HelloPython.py

$ python 01-HelloPython.py

printIs the pythonfirst we learned of the function

printAction function, you can put "" the contents inside, and output to the screen

1.3 Extended Walkthrough - Mistake (BUG)

About error

• Programs written can not be executed properly , or execution result is not what we expected
• Commonly known BUG, is a programmer in the development of very common, common mistakes beginners reasons include:
  1. mistake
  2. Already learned knowledge to understand there are still insufficient
  3. There is need for content and promotion of language learning
• When learning a language, not only to learn the syntax of the language , but also learn how to recognize errors and methods to resolve errors

Every programmer is growing constantly correct errors in

Common Errors first walkthrough

• 1> wrong hands , for example,pirnt("Hello world")

NameError: name 'pirnt' is not defined

名称错误：'pirnt' 名字没有定义

• 2> The number of printwrite in a row

SyntaxError: invalid syntax

语法错误：语法无效

Every line of code responsible for completing an action

• 3> indentation errors

IndentationError: unexpected indent

缩进错误：不期望出现的缩进

• Python is a very strict format programming language
• For now, we remember the front of each line of code do not add a space

• 4> Python 2.x default does not support Chinese

There are two versions of Python coexist on the market, respectively, Python 2.xandPython 3.x

• Python 2.x default does not support Chinese , the specific reasons, until the introduction character encoding when to explain to
• Python 2.x interpreter name is python
• Python 3.x interpreter name is python3

SyntaxError: Non-ASCII character '\xe4' in file 01-HelloPython.py on line 3, 
but no encoding declared; 
see http://python.org/dev/peps/pep-0263/ for details

语法错误： 在 01-HelloPython.py 中第 3 行出现了非 ASCII 字符 '\xe4'，但是没有声明文件编码
请访问 http://python.org/dev/peps/pep-0263/ 了解详细信息

• ASCIICharacter contains only 256characters, does not support Chinese
• Issues related to character encoding, follow-up will speak

Word list

* error 错误
* name 名字
* defined 已经定义
* syntax 语法
* invalid 无效
* Indentation 索引
* unexpected 意外的，不期望的
* character 字符
* line 行
* encoding 编码
* declared 声明
* details 细节，详细信息
* ASCII 一种字符编码

02. Python 2.xand 3​​.xversion Introduction

There are two versions of Python coexist on the market, respectively, Python 2.xandPython 3.x

The new program is recommended to use Python Python 3.0version syntax

• Python 2.x is the last version
  • Interpreter name is python
• Python 3.x is now mainstream and future versions
  • Interpreter name is python3
  • With respect to the Pythonearlier version, which is a major upgrade
  • In order not to bring too much burden, Python 3.0when the design does not consider backward compatible
    • Many of the early Pythonversions of the design of the program can not be in Python 3.0the normal execution on
  • Python 3.0 released in 2008
  • So far, Python version 3.0 has been stable for many years
    • Python 3.3 released in 2012
    • Python 3.4 released in 2014
    • Python 3.5 released in 2015
    • Python 3.6 released in 2016
• In order to take care of existing programs, it provides a transition official version - Python 2.6
  • Use the basic Python 2.xsyntax and libraries
  • Taking into account the Python 3.0migration, allowing the use of part of the Python 3.0 syntax and function
  • Launched in 2010, Python 2.7it was identified as the last Python 2.x version

Tip: If the developer can not be used immediately Python 3.0 (there are very few third-party libraries do not support syntax 3.0), it is recommended

• First use Python 3.0version developed
• Then Python 2.6, Python 2.7to perform, and to make the processing of some compatibility

03. Python implementation of the program in three ways

3.1. Interpreter python/python3

Python interpreter

# 使用 python 2.x 解释器
$ python xxx.py

# 使用 python 3.x 解释器
$ python3 xxx.py

Other interpreters (to know)

Python interpreter now have to implement multiple languages, including:

• CPython - the official version of the C language
• Jython - you can run on the Java platform
• IronPython - it can run on .NET and Mono platforms
• PyPy - Python, support for real-time JIT compiler

3.2. The interactive program run Python

• Run the interpreter in the terminal directly, without entering the file name to be executed
• In Python's Shelldirect input in Python code , the program will immediately see the results

1) Interactive run Python's strengths and weaknesses

advantage

• Suitable for learning / verification codes or locally Python syntax

Shortcoming

• Code can not be saved
• Not suitable for running much of the program

2) Quit official interpreter

1> Direct Input exit()

>>> exit()

2> using a hotkey to exit

In the python interpreter, press the hotkey ctrl + dto exit the interpreter

3) IPython

• IPython in the "I" represents the interaction interactive

Feature

• IPython is a python's interactive shell , than the default python shellmuch more useful
  • It supports auto-completion
  • Auto-indenting
  • Support bash shellCommand
  • It built a lot of features and useful functions
• IPython is based on the BSD open source

version

• Python 2.x interpreter is used ipython

• Python 3.x interpreter is used ipython3

• To exit the interpreter can have the following two ways:

1> Direct Input exit

In [1]: exit

2> using a hotkey to exit

In IPython interpreter, press the hot key ctrl + d, IPythonit will be asked whether to exit the interpreter

IPython installed

$ sudo apt install ipython

. 3.3 Python of IDE - PyCharm

1) Integrated Development Environment (IDE)

Integrated Development Environment ( IDE, Integrated Development Environment) - integrates all the tools needed to develop software generally includes the following tools:

• GUI
• Code Editor (supports code completion / auto-indent )
• Compiler / interpreter
• Debugger ( breakpoints / stepping )
• ……

2) PyCharm Introduction

• PyCharm The Python is a very good integrated development environment
• PyCharmIDE necessary for addition to the general functions, but also in Windows, Linux, macOSthe use of
• PyCharm Suitable for large-scale development projects
  • A project usually contains several files
  • Each source code line number is limited, usually within a few hundred lines of
  • Each source file their duties together to accomplish complex business functions

3) PyCharm quickly experience

• File navigation area can browse / locate / open the project file

• Document editing area can edit the currently open file

• Console area to:

  • Output program execution content
  • Execution trace debugging code

• The upper right corner of the toolbar can execute (the SHIFT + F10) / Debug (SHIFT + F9) Code

• The console above the single-step execution button (the F8) , can step through the code