1 def add(n,i):
 2     return n+i
 3 
 4 def test():
 5     for i in range(4):
 6         yield i
 7 
 8 g=test()
 9 
10 for n in [1,2,3]:
11     g=(add(n,i) for i in g)
12 #等价于
13 #####
14 n = 1
15 g=(add(n,i) for i in g)
16 n = 2
17 g=(add(n,i) for i in g)
18 n = 3
19 g=(add(n,i) for i in g)
20 #####
21 n = 1
22 g=(add(n,i) for i in g)
23 n = 2
24 g=(add(n,i) for i in (add(n,i) for i in g))
25 n = 3
26 g=(add(n,i) for i in (add(n,i) for i in (add(n,i) for i in g)))
27 #####
28 n = 1
29 g=(add(n,i) for i in g)
30 n = 2
31 g=(add(n,i) for i in (add(n,i) for i in g))
32 n = 3
33 g=(add(n,i) for i in (add(n,i) for i in (add(n,i) for i in test())))
34 #test()  (0,1,2,3)
35 #####
36 n = 1
37 g=(add(n,i) for i in g)
38 n = 2
39 g=(add(n,i) for i in (add(n,i) for i in g))
40 n = 3
41 g=(add(n,i) for i in (add(n,i) for i in (add(3,i) for i in (0,1,2,3))))
42 #####
43 n = 1
44 g=(add(n,i) for i in g)
45 n = 2
46 g=(add(n,i) for i in (add(n,i) for i in g))
47 n = 3
48 g=(add(n,i) for i in (add(3,i) for i in (3,4,5,6)))
49 #####
50 n = 1
51 g=(add(n,i) for i in g)
52 n = 2
53 g=(add(n,i) for i in (add(n,i) for i in g))
54 n = 3
55 g=(add(3,i) for i in (6,7,8,9))
56 #####
57 
58 print(list(g))