Python学习（十五）：字符串的格式化

Python学习（十五）：字符串的格式化

这是我关于Python学习的第十五篇博客，加油！

字符串格式化：

将字符串按照一定规则进行拼接，有两种常见方式，分别是%方式和format方式

1. %方式

（1）%s，拼接的为字符串，其实也可拼接数字，列表,+表示左对齐，-表示右对齐，数字表示占据多少字符

n='i am %+60s,my hobby is %-20s'% ('alex','reading')
n1='i am %s,my hobby is %s'% (567,[1,2,'alex'])
print(n,n1)
'''
i am                                                         alex,my hobby is reading              
i am 567,my hobby is [1, 2, 'alex']
'''

（2）%d，拼接数字，只能拼接数字

n='my age is %d'%(20)
print(n)#my age is 20

若是实际应用，可在百分号后输入变量，这样方便一些

name='alex'
hobby='reading'
n='i am %s,my hobby is %s'% (name,hobby)
print(n)#i am alex,my hobby is reading

也可这样写

n='i am %(name)s,my hobby is %(hobby)s'% {'name':'alex','hobby':'reading'}
print(n)#i am alex,my hobby is reading

（3）%f，浮点数，可在%和f之间加入.x，x指的是数字，这样就可以设置打印出的浮点数保留几位小数（会进行四舍五入），不设置时通常默认保留六位小数

tpl='percent %f'%99.97845623
tpl1='percent %.8f'%99.97845623
tpl2='percent %.2f'%99.97845623
print(tpl,tpl1,tpl2)#percent 99.978456 percent 99.97845623 percent 99.98

（4）%%，百分比

tpl='percent %f%%'%99.97845623
tpl1='percent %.8f%%'%99.97845623
tpl2='percent %.2f%%'%99.97845623
print(tpl,tpl1,tpl2)#percent 99.978456% percent 99.97845623% percent 99.98%

2. format方式
   （1）一一对应（若没有对应，则会报错），往大括号内传值

n='i am {}, age {},i like {}'.format('alex','18','reading')
print(n)

（2）使用下标使其对应，这时format后面的括号就是元组的形式，可以对同一个值取多次

n='i am {2}, age {0},i like {1}'.format('alex','18','reading')
print(n)#i am reading, age alex,i like 18
n1='i am {2}, age {2},i like {2}'.format('alex','18','reading')
print(n1)#i am reading, age reading,i like reading

（3）使用字典形式，如果是纯粹的字典形式，即format后用的是大括号的话，必须在大括号前加入两个*

n='i am {name}, age {age},i like {hobby}'.format(name='alex',age='18',hobby='reading')
n1='i am {name}, age {age},i like {hobby}'.format(**{'name':'alex','age':'18','hobby':'reading'})
print(n,n1)

（4）使用索引

n='i am {0[0]}, age {1[2]},i like {0[1]}'.format([1,2,3],[5,6,7])
print(n)#i am 1, age 7,i like 2

（5）使用**：**，此处的：作用与%相似

n='i am {:s}, age {:d},i like {:f}'.format('alex',18,98.25467456)
print(n)#i am alex, age 18,i like 98.254675

（6）使用：，当format后为列表时，在列表前加入一个*，*代表遍历，有点像for的作用

n='i am {0}, age {1},i like {2}'.format(*['alex',18,98.25467456])
print(n)#i am alex, age 18,i like 98.25467456
l=['alex',18,98.25467456]
n='i am {0}, age {1},i like {2}'.format(*l)
print(n)#i am alex, age 18,i like 98.25467456