yield生成器及字符串的格式化

一、生成器

 1 def ran():
 2     print(‘Hello world‘)
 3     yield ‘F1‘
 4
 5     print(‘Hey there!‘)
 6     yield ‘F2‘
 7
 8     print(‘goodbye‘)
 9     yield ‘F3‘
10
11 ret = ran() # ran()称为生成器函数，ret才是生成器，仅仅具有一种生成能力，函数内部要有关键字yield
12 print(ret)
13
14 res = ret.__next__() #对生成器进行循环操作，遇到yield会停止操作，将yield的值返回给变量，并会记录保存位置
15 print(res)
16
17 res1 = ret.__next__() #下次再对生成器进行操作，会从停止出开始，直到下一个yield停止
18 print(res1) # 当__next__次数超过yield时，会报错
19
20 for i in ret: #进行__next__之后再进行for循环，也是从上次yield停止处开始
21     print(i)

二、字符串的格式化

① % 方法

 1 s = ‘I am a %s guy‘ % (‘good‘)
 2 print(s)
 3
 4 n = ‘I am a %s guy,%d years old‘ % (‘good‘,28)
 5 print(n)
 6
 7 d = ‘I am a %(n1)s guy,%(n2)d years old‘ % {‘n1‘:"good",‘n2‘:28}
 8 print(d)
 9
10 f = ‘I am %f‘ % (28) # 浮点数占位符，默认保留小数点后6位，四舍五入
11 print(f)
12
13 f1 = ‘I am %.2f‘ % (28) #设置保留小数点后2位
14 print(f1)
15
16 # typecode
17 %s : 字符串
18 %d : 十进制数字
19 %f ：浮点型
20 %% ：%
21 %o : 将十进制转换成八进制返回
22 %x ：将十进制转换成十六进制返回
23 %e ：将数字转换成科学记数法

② format方法

 1 tem = ‘I am {},age {},‘.format(‘Ethan‘,28)
 2 print(tem)
 3
 4 tem = ‘I am {},age {},{}‘.format(*[‘Ethan‘,28,‘Ethan‘])
 5 print(tem)
 6
 7 tem = ‘I am {0},age {1},really {0}‘.format(‘Ethan‘,28)
 8 print(tem)
 9
10 tem = ‘I am {0},age {1},really {0}‘.format(*[‘Ethan‘,28])
11 print(tem)
12
13 tem = ‘I am {name},age {age},really {name}‘.format(**{‘name‘:‘Ethan‘,"age":28})
14 print(tem)
15
16 tem = ‘I am {name},age {age},really {name}‘.format(name = ‘Ethan‘,age = 28)
17 print(tem)
18
19 tem = ‘I am {0[0]},age {0[1]},really {0[0]}‘.format([‘Ethan‘,28],[‘Seven‘,27])
20 print(tem)
21
22 tem = ‘I am {:s},age {:d},money {:f}‘.format(‘Ethan‘,28,8988.23)
23 print(tem) # I am Ethan,age 28,money 8988.230000
24
25 tem = ‘I am {:s},age {:d}‘.format(*[‘Ethan‘,28])
26 print(tem)
27
28 tem = ‘I am {name:s},age {age:d}‘.format(age = 28,name = ‘Ethan‘)
29 print(tem)
30
31 tem = ‘I am {name:s},age {age:d}‘.format(**{‘name‘:‘Ethan‘,‘age‘:28})
32 print(tem)
33
34 tem = ‘Numbers:{:b},{:o},{:d},{:x},{:X},{:%}‘.format(15,15,15,15,15,15.87623,2)
35 print(tem) # Numbers:1111,17,15,f,F,1587.623000%