python基础---->字符串格式化

关于字符串格式化

Python的字符串格式化有两种方式: %方式、format方式；

百分号的方式相对来说比较过时，而format方式则是比较先进的方式，企图替换古老的方式，目前两者并存。

1、百分号方式

官方文档对其说明的格式，更详细请参考：[PEP-3101]

%[(name)][flags][width].[precision]typecode

(name)      可选，用于选择指定的key；
flags          可选；
width         可选，占有宽度；
.precision   可选，小数点后保留的位数；
typecode    必选；    

百分号格式化常用实例：

exp = "i am %s" % "clint"
 
exp = "i am %s age %d" % ("clint", 18)
 
exp= "i am %(name)s age %(age)d" % {"name": "clint", "gender": 18}
 
exp = "percent %.2f" % 123.456789
 
exp = "i am %(a).2f" % {"a": 123.4567890, }
 
exp = "i am %.2f %%" % {"a": 123.4567890, }

2、Format方式

[[fill][align][sign][#][0][width][,][.precision][type]

fill           【可选】空白处填充的字符
align        【可选】对齐方式（需配合width使用）
sign         【可选】有无符号数字
#            【可选】对于二进制、八进制、十六进制，如果加上#，会显示 0b/0o/0x，否则不显示
，            【可选】为数字添加分隔符，如：1,000,000
width       【可选】格式化位所占宽度
.precision 【可选】小数位保留精度
type         【可选】格式化类型

Format格式化常用实例：

exp = "i am {}, age {}".format("clint", 18)
  
exp  = "i am {}, age {}, {}".format(*["clint", 18, 'clinton])
  
exp = "i am {0}, age {1}, really {0}".format("clint", 18)
  
exp = "i am {0}, age {1}, really {0}".format(*["clint", 18])
  
exp = "i am {name}, age {age}, really {name}".format(name="clint", age=18)
  
tpl = "i am {name}, age {age}, really {name}".format(**{"name": "clint", "age": 18})
  
exp = "i am {0[0]}, age {0[1]}, really {0[2]}".format([1, 2, 3], [11, 22, 33])
  
exp = "i am {:s}, age {:d}, money {:f}".format("clint", 18, 88888.1)
  
exp = "i am {:s}, age {:d}".format(*["clint", 18])
  
tpl = "i am {name:s}, age {age:d}".format(name="clint", age=18)
  
exp = "i am {name:s}, age {age:d}".format(**{"name": "clint", "age": 18})
 
exp = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
 
exp = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
 
exp = "numbers: {0:b},{0:o},{0:d},{0:x},{0:X}, {0:%}".format(15)
 
exp  = "numbers: {num:b},{num:o},{num:d},{num:x},{num:X}, {num:%}".format(num=15)