Python-enhanced formatted string format function

Grammar

It replaces% with {} and:.

Map sample

By location

In [1]: ‘{0},{1}‘.format(‘kzc‘,18)  Out[1]: ‘kzc,18‘  In [2]: ‘{},{}‘.format(‘kzc‘,18)  Out[2]: ‘kzc,18‘  In [3]: ‘{1},{0},{1}‘.format(‘kzc‘,18)  Out[3]: ‘18,kzc,18‘

字符串的format函数可以接受不限个参数，位置可以不按顺序，可以不用或者用多次，不过2.6不能为空{}，2.7才可以。

通过关键字参数

In [5]: ‘{name},{age}‘.format(age=18,name=‘kzc‘)  Out[5]: ‘kzc,18‘

通过对象属性

class Person:      def __init__(self,name,age):          self.name,self.age = name,age          def __str__(self):              return ‘This guy is {self.name},is {self.age} old‘.format(self=self)  

In [2]: str(Person(‘kzc‘,18))  Out[2]: ‘This guy is kzc,is 18 old‘

by subscript

In [7]: p=[‘kzc‘,18]In [8]: ‘{0[0]},{0[1]}‘.format(p)Out[8]: ‘kzc,18‘

有了这些便捷的“映射”方式，我们就有了偷懒利器。基本的Python知识告诉我们，list和tuple可以通过“打散”成普通参数给函数，而dict可以打散成关键字参数给函数（通过和*）。所以可以轻松的传个list/tuple/dict给format函数。非常灵活。

Format qualifier

It has a rich "format qualifier" (syntax is {} with:), such as:

fill and align
Padding is used in conjunction with alignment
^, <, > center, Align Left, right, back with width
: The fill character after the number, only one character, not specified by default is filled with a space
Like what

In [15]: ‘{:>8}‘.format(‘189‘)Out[15]: ‘     189‘In [16]: ‘{:0>8}‘.format(‘189‘)Out[16]: ‘00000189‘In [17]: ‘{:a>8}‘.format(‘189‘)Out[17]: ‘aaaaa189‘

accuracy and type F
Accuracy is often used in conjunction with Type F

In [44]: ‘{:.2f}‘.format(321.33345)Out[44]: ‘321.33‘

其中.2表示长度为2的精度，f表示float类型。

Other types

主要就是进制了，b、d、o、x分别是二进制、十进制、八进制、十六进制。

In [54]: ‘{:b}‘.format(17)Out[54]: ‘10001‘In [55]: ‘{:d}‘.format(17)Out[55]: ‘17‘In [56]: ‘{:o}‘.format(17)Out[56]: ‘21‘In [57]: ‘{:x}‘.format(17)Out[57]: ‘11‘

Use, the number can also be used to make the amount of thousands separator.

in [+]: ' {:,} '. Format (1234567890) out[47]: ' 1,234,567,890 '

Python-enhanced formatted string format function