%和format

格式化字符串主要有两种
<code>% 和 format</code>
但format是2.6之后的新特性。
so，推荐format

1，区别

demo：

# 坐标
c = (1, 2)
s1 = '坐标:%s' % c

这样便会报错：<code>TypeError: not all arguments converted during string formatting</code>

需要再进行修改，如示，%和format

s2 = '坐标:%s' % (c,)
print(s1)    # 坐标:[1, 2]

s1 = '坐标:{}'.format(c)
print(s1)    # 坐标:[1, 2]

2，新特性f-strings，仅限3.6以后

name = "tom"
age = 10
a = f"name:{name},age:{aeg}"
print(a)

常用语法

0，默认传值

print("name:{},age:{}".format("tom",18))
# name:tom,age:10

1，通过位置

date = ['tom',18]
print("name:{0},age:{1}".format(*data))
# name:tom,age:10

2，通过关键字，即数据是字典序

data = {"name": "tom", "age": 18}
print("name:{name},age:{age}".format(**data))
# name:tom,age:18

3，通过下标

data = ['tom', 10]
print("{0[0]} is {0[1]} year old".format(data))
# tom is 10 year old

4，通过对象属性

class Person(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def __str__(self):
        return "name:{self.name}, age:{self.age}".format(self=self)

p = Person("tom", 18)
print(str(p))
# name:tom, age:18

5，精度和类型

a = "{:.2f}".format(3.1415926)
print(a)
# 3.14

6，千位分隔符

a = "{:,}".format(1234567890)
print(a)
# '1,234,567,890'

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