yield用法

yield的__next__()和send()的用法，詳見代碼

 

 1 def D():
 2     n = 1
 3     while n < 5:
 4         m = yield n
 5         print("m:",m)
 6         print("n:",n)
 7         n += 4
 8         yield 10
 9         yield
10 
11 d = D()
12 # __next__() 是尋找下一個yield，並將yield後面的值返回,右面沒值，則返回None,若是沒找到yield 就報錯,__next__()不給yield傳值
13 # j = d.__next__()
14 # print(j)
15 # j = d.__next__()
16 # print(j)
17 
18 # send(x)是返回上一個中斷的yield，並將值傳給yield,而後尋找下一個yield,並將yield後面的值返回,若是沒找到下一個yield，就報錯
19 # 若是在這以前沒有開啓generator，則只能傳遞None值給yield (使用 send(None))，並當即返回yield後面的值
20 # j = d.send(3)  # TypeError: can't send non-None value to a just-started generator
21 
22 def exam1():
23     j = d.send(None)   # j = 1 ， 返回的是第一次遇到yield後 n的值
24     print(j)    # j = 1
25     #
26     # 1
27     j = d.send(3)
28     print(j)
29     # 1
30     # m: 3
31     # n: 1
32     # 10
33     j = d.__next__()
34     print(j)
35     # 1
36     # m: 3
37     # n: 1
38     # 10
39     # 4
40     j = d.send(20)