Python 扩展知识：格式化输出

常见的格式符：

  %s ：字符串 ( 采用 str() 的显示 )
  %r ：字符串 ( 采用 repr() 的显示 )
  %d ：整数 ( 十进制 )
  %f ：浮点数

示例1：

In [1]: name = "Tom"

In [2]: age = 20

In [3]: "My name is %s" % name      
Out[3]: 'My name is Tom'

In [4]: "My name is %r" % name 
Out[4]: "My name is 'Tom'"

In [5]: "My age is %d" % age
Out[5]: 'My age is 20'

In [6]: "My age is %f" % age 
Out[6]: 'My age is 20.000000'

In [7]: "My age is %.3f" % age
Out[7]: 'My age is 20.000'