1. Python 变量 及 运算

Numbers

int 整数类型 如 : (2 , 4 , 20)
float 浮点类型 如 : (5.0 , 1.6)

>>> 2 + 2
4
>>> 50 - 5*6
20
>>> (50 - 5*6) / 4
5.0
>>> 8 / 5  # 除法总是返回浮点类型
1.6

运算符
/ : 返回浮点类型
// : 返回整数部分
% : 返回余数

>>> 17  /  3   
5.666666666666667 
>>> 
>>> 17  //  3   
5 
>>> 17  ％ 3   
2 
的剩余部分>> > 5  *  3  +  2   

** : 计算平方数

>>> 5  **  2   ＃5
25 
>>> 2  **  7   ＃2的7次方
128 

= : 用于赋值给一个变量 .

>>> width  =  20 
>>> height  =  5  *  9 
>>> width  *  height 
900

混合运算会将结果返回为浮点型

>>> 4 * 3.75 - 1
14.0

Strings

字符串可以使用单引号('...')和双引号("...")表示
\ : 表示单个引号的(')转义符 , 或者使用 双引号("...")

>>> 'spam eggs'  # single quotes
'spam eggs'
>>> 'doesn\'t'  # use \' to escape the single quote...
"doesn't"
>>> "doesn't"  # ...or use double quotes instead
"doesn't"
>>> '"Yes," he said.'
'"Yes," he said.'
>>> "\"Yes,\" he said."
'"Yes," he said.'
>>> '"Isn\'t," she said.'
'"Isn\'t," she said.'

r : 显示原字符串

>>> print('C:\some\name')  # here \n means newline!
C:\some
ame
>>> print(r'C:\some\name')  # note the r before the quote
C:\some\name

"""...""" 和 '''...''' : 字符串跨行 , 行尾自动包含在字符串中 , 可以通过在行尾添加 \ 来防止这种情况

>>>print("""\
>>>Usage: thingy [OPTIONS]
>>>     -h                        Display this usage message
>>>     -H hostname               Hostname to connect to
>>>""")

Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to

+ : 字符串拼接

>>> # 3 times 'un', followed by 'ium'
>>> 3 * 'un' + 'ium'
'unununium'

相邻的字符串会自动拼接在一起

>>> 'Py' 'thon'
'Python'