1 Python2.X和Python3.X的区别 2  3 What are the differences? 4  5 Short version: Python 2.x is legacy, Python 3.x is the present and future of the language 6  7 Python 3.0 was released in 2008. The final 2.x version 2.7 release came out in mid-2010, with a statement of extended support for this end-of-life release. The 2.x branch will see no new major releases after that. 3.x is under active development and has already seen over five years of stable releases, including version 3.3 in 2012, 3.4 in 2014, and 3.5 in 2015. This means that all recent standard library improvements, for example, are only available by default in Python 3.x. 8  9 Guido van Rossum (the original creator of the Python language) decided to clean up Python 2.x properly, with less regard for backwards compatibility than is the case for new releases in the 2.x range. The most drastic improvement is the better Unicode support (with all text strings being Unicode by default) as well as saner bytes/Unicode separation.10 11 Besides, several aspects of the core language (such as print and exec being statements, integers using floor division) have been adjusted to be easier for newcomers to learn and to be more consistent with the rest of the language, and old cruft has been removed (for example, all classes are now new-style, "range()" returns a memory efficient iterable, not a list as in 2.x).12 13 The What‘s New in Python 3.0 document provides a good overview of the major language changes and likely sources of incompatibility with existing Python 2.x code. Nick Coghlan (one of the CPython core developers) has also created a relatively extensive FAQ regarding the transition.14 15 However, the broader Python ecosystem has amassed a significant amount of quality software over the years. The downside of breaking backwards compatibility in 3.x is that some of that software (especially in-house software in companies) still doesn‘t work on 3.x yet. 16 17 详细地址：https://wiki.python.org/moin/Python2orPython318 19 - 区别一：20         Python2：print ‘Hellow world!‘21         Python3: print (‘Hellow world!‘)22 - 区别二：23         Python2:raw_input24         Python3:input

1 - IDE中执行：2     print ("Hello world!")3 - Linux环境,将"print (‘Hello world!‘)"代码写入到first.py文件中：4     python first.py5 - 指定解释器执行：6     #/usr/bin/env python7     print (‘Hello world!‘)8     chmod +x first.py9     ./first.py

  1   2   4   8   16  ....    65535  1   1   1   1   1   ....    1*16

 #-*- coding:uft-8 -*- #-*- coding:gbk -*-

- asscii码  255 1bytes  一个字符占8个字节- unicode万国码 2bytes- utf-8 en:1byte cn:3bytes

- [1] 变量名只能是 字母、数字或下划线的任意组合- [2] 变量名的第一个字符不能是数字- [3] 以下关键字不能声明为变量名    [‘and‘, ‘as‘, ‘assert‘, ‘break‘, ‘class‘, ‘continue‘, ‘def‘, ‘del‘, ‘elif‘, ‘else‘, ‘except‘, ‘exec‘, ‘finally‘, ‘for‘, ‘from‘, ‘global‘, ‘if‘, ‘import‘, ‘in‘, ‘is‘, ‘lambda‘, ‘not‘, ‘or‘, ‘pass‘, ‘print‘, ‘raise‘, ‘return‘, ‘try‘, ‘while‘, ‘with‘, ‘yield‘]- [4] 写法    age_of_oldboy = 56    ageOfOldboy = 56 #驼峰写法    AGE_OF_OLDBOY = 56 #常量,定义不变的量

单行注释:#多行注释:"""或者‘‘‘多行字符串:""" (标注段落)

****Python默认输入都是字符串****int()   #interger,字符串转数字str()   #string,数字转字符串type()  #查看数据类型:print(type())

 1 %s 变量可以是字符和数字(string) 2 %d 变量只能是数字,可以用来检测数据类型 3 %f 变量只能是小数(浮点型) 4  5 方案一： 6 name = input("name:") 7 age = input("age:") 8 job = input("job:") 9 salary = input("salary:")10 11 info = ‘‘‘12 -----info of ‘‘‘+name+‘‘‘----13 Name:‘‘‘+name+‘‘‘14 Age:‘‘‘+age+‘‘‘15 Job:‘‘‘+job+‘‘‘16 Salary:‘‘‘+salary+‘‘‘17 ‘‘‘18 print(info)19 20 方案二：21 name = input("name:")22 age = input("age:")23 job = input("job:")24 salary = input("salary:")25 26 info = ‘‘‘27 ------ info of %s------28 Name:%s29 Age:%s30 Job:%s31 Salary:%s32 ----------END----------‘‘‘%(name,name,age,job,salary)33 print(info)34 35 方案三:36 name = input("name:")37 age = input("age:")38 job = input("job:")39 salary = input("salary:")40 41 info2 = ‘‘‘42 ------ info of {_name}------43 Name:{_name}44 Age:{_age}45 Job:{_job}46 Salary:{_salary}47 ‘‘‘.format(_name=name,_age=age,_job=job,_salary=salary)48 print(info2)49 50 方案四：51 name = input("name:")52 age = input("age:")53 job = input("job:")54 salary = input("salary:")55 info2 = ‘‘‘56 -----info of {0}-----57 Name:{0}58 Age:{1}59 Job:{2}60 Salary:{3}61 ------END----‘‘‘.format(name,age,job,salary)62 print(info2)

 1 Ctrl / 2  3 注释(取消注释)选择的行 4  5  6 Shift + Enter 7 开始新行 8  9 Ctrl + Enter10 智能换行11 12 TAB Shift+TAB13 缩进/取消缩进所选择的行14 15 Ctrl + Alt + I16 自动缩进行17 18 Ctrl + Y19 删除当前插入符所在的行20 21 Ctrl + D22 复制当前行、或者选择的块23 24 Ctrl + Shift + J25 合并行26 27 Ctrl + Shift + V28 从最近的缓存区里粘贴29 30 Ctrl + Delete31 删除到字符结尾32 33 Ctrl + Backspace34 删除到字符的开始35 36 Ctrl + NumPad+/-37 展开或者收缩代码块38 39 Ctrl + Shift + NumPad+40 展开所有的代码块41 42 Ctrl + Shift + NumPad-43 收缩所有的代码块