pyhton中format函数用法

从代码中看其使用方法：

#通过位置
print('{0},{1}'.format('csdn',20))

print ('{},{}'.format('csdn',20))

print ('{1},{0},{1}'.format('csdn',20))

#通过关键字参数
print('{name},{age}'.format(age=18,name='csdn'))

class Person:
    def __init__(self,name,age):
        self.name = name
        self.age = age

    def __str__(self):
        return 'This guy is {self.name},is {self.age} old'.format(self=self)

print (str(Person('csdn',18)))

#通过映射 list
a_list = ['csdn',20,'china']
print('my name is {0[0]},from {0[2]},age is {0[1]}'.format(a_list))
#my name is chuhao,from china,age is 20

#通过映射 dict
b_dict = {'name':'chuhao','age':20,'province':'shanxi'}
print ('my name is {name}, age is {age},from {province}'.format(**b_dict))
#my name is chuhao, age is 20,from shanxi

#填充与对齐
print ('{:>8}'.format('234'))
#     189
print ('{:0>8}'.format('234'))
#00000189
print ('{:a>8}'.format('234'))
#aaaaa189

#精度与类型f
#保留两位小数
print ('{:.2f}'.format(321.33345))
#321.33

#用来做金额的千位分隔符
print ('{:,}'.format(1234567890))
#1,234,567,890

#其他类型 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。

print('{:b}'.format(18) )#二进制 10010)

运行结果：

csdn,20
csdn,20
20,csdn,20
csdn,18
This guy is csdn,is 18 old
my name is csdn,from china,age is 20
my name is chuhao, age is 20,from shanxi
     234
00000234
aaaaa234
321.33
1,234,567,890
10010