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format格式化

1,基本格式

#对于每一个大括号，在后面的参数中找到对应的参数插进来
#format操作类似于于将传入的参数制成多个数据的数据结构元组或者字典，然后依照索引插入参数
s = "i am {},i am {} years old ,i like {}".format("haiyang",20,"zhu")
print(s)
s = "i am {},i am {} years old ,i like {}".format("haiyang","20","zhu")
print(s)

i am haiyang,i am 20 years old ,i like zhui am haiyang,i am 20 years old ,i like zhu

2，定义变量的索引

s = "i am {2},i am {1} years old ,i like {0}".format("haiyang",20,"zhu")
print(s)

i am zhu,i am 20 years old ,i like haiyang

3，定义变量名称

#类似于索引，只不过这里的索引变成了自定义的索引，不再是0-...因此需要传入字典
s = "i am {name},i am {age} years old ,i like {girl}".format(name="haiyang",age=20,girl="zhu")
print(s)

i am haiyang,i am 20 years old ,i like zhu

4，控制输出长度和格式

s = "i am {:.2s},i am {:d} years old ,i like {:.2f}".format("haiyang",20,22.231231321)
print(s)

i am ha,i am 20 years old ,i like 22.23

5，格式化传入数据的格式需求

在format等类似的函数中，会默认你传入的是一组数据，这是函数边长参数的相关知识
但是如果你直接将一组数据制成链表形式的数据格式传入，则需要通知，否则会将传入的列表当做一
个元素处理而不会去遍历列表中的元素
比如第一种，需要传入的数据类似于元组，如果想直接传入一个元组，则需要用*标识,否则会报错

tmp = ("haiyang",20,"zhu")
s = "i am {},i am {} years old ,i like {}".format(*tmp)
print(s)
s = "i am {},i am {} years old ,i like {}".format(tmp)
print(s)

i am haiyang,i am 20 years old ,i like zhu
---------------------------------------------------------------------------

IndexError                                Traceback (most recent call last)

<ipython-input-5-bfc251778bb3> in <module>()
4 s = "i am {},i am {} years old ,i like {}".format(*tmp)
5 print(s)
----> 6 s = "i am {},i am {} years old ,i like {}".format(tmp)
7 print(s)

IndexError: tuple index out of range

如果需要传入字典而你已经把字典做好了，就需要用**标识一下，否则也会报错

dic = {"name":"haiyang","age":20,"girl":"zhu"}
s = "i am {name},i am {age} years old ,i like {girl}".format(**dic)
print(s)
s = "i am {name},i am {age} years old ,i like {girl}".format(dic)
print(s)

i am haiyang,i am 20 years old ,i like zhu
---------------------------------------------------------------------------

KeyError                                  Traceback (most recent call last)

<ipython-input-9-ffa4c40a411c> in <module>()
3 s = "i am {name},i am {age} years old ,i like {girl}".format(**dic)
4 print(s)
----> 5 s = "i am {name},i am {age} years old ,i like {girl}".format(dic)
6 print(s)

KeyError: 'name'

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