元哥3天学Python--Day1

• 学习资料：
  Python3 Tutorial

1. Interactive Shell

terminal$ python3
>>>

2. Execute .py Script

python fileName.py

Python is both an interpreted and a compiled language.

Python会自动检查工作目录的写权限，如果没有写权限，那么编译的代码只会在程序执行的时候产生，程序退出，编译的代码就会被消除（相当于直接interpret而“未compile”）。如果有写权限，那么编译的代码就会被存在.pyc文件中。

编译的代码由PVM执行。

Compiler: to transform source code into executable program

Interpreter: (1) execute the source code directly or (2) translates the source code in a first step into a more efficient representation and executes this code

3. Python structures by colons and indentation

从语法上保证了程序的易读性

4. Variables

1. Numbers

Integer, Floating, Complex

• There is no "long int" in Python3 anymore, Integers in Python3 can be of unlimited size.
• true div: /; floor div: //

2. String

• All strings in Python 3 are sequences of "pure" Unicode characters

• ASCII: 128 characters
• Unicode: four bytes are possible per character

• Immutable

• 比较

• is 比地址；==比内容
• 一个奇怪之处：

"Hi" is "Hi" == true 
"Hi!" is "Hi!" == False //含特殊字符

5. Operators

10 / 3 == 3.3333333333333335
10 // 3 == 3
10.0 // 3 == 3.0
10**3 == 1000