Ｐｙｔｈｏｎ之切片、迭代

 1 #迭代
 2 d = {'s':1,'b':2,'c':3};
 3 #默认情况下,迭代的对象是ｋｅｙ，如果要迭代ｖａｌｕｅ，用for value in d.values(),如果要同时迭代key 和　value ，可以用for k,v in d.items()
 4 print("迭代key")
 5 for key in d:
 6     print(key)
 7 
 8 print("迭代value")
 9 for value in d.values():
10     print(value)
11 
12 print("迭代key 和　value")
13 for k,v in d.items():
14     print(k,v)
15 
16 ###迭代字符窜
17 print("迭代字符串")
18 for ch in 'ABC':
19     print(ch)
20 
21 ######如何判断对象是否可迭代＃＃＃＃＃＃＃＃
22 from collections import Iterable
23 abc = isinstance('abc',Iterable)
24 print("str 是否可迭代：")
25 print(abc)
26 
27 my_list = isinstance([1,2,3],Iterable)
28 print("list 是否可迭代：")
29 print(my_list)
30 
31 my_123 = isinstance(123,Iterable)
32 print("整数是否可迭代：")
33 print(my_123)
34 
35 ########利用　enumerate 函数将list 变成索引－元素对，实现下标循环＃＃＃＃＃＃
36 print("利用enumerate 实现索引和元素的同时迭代：")
37 for i,value in enumerate(['A','B','C']):
38     print(i,value)
39 
40 print("Python　中　for 循环中同时用两个变量：")
41 for x,y in [(1,1),(2,4),(3,9)]:
42     print(x,y)
43 
44 def findMinAndMax(L):
45     #print(len(L))
46     if len(L)<=0:
47         return (None,None)
48     else:
49         Min = L[0]
50         Max = L[0]
51         for value in L[1:]:
52             if value < Min:
53                 Min = value
54             if value > Max:
55                 Max = value
56         return(Min,Max)
57 
58 # 测试
59 if findMinAndMax([]) != (None, None):
60      print('测试失败!')
61 elif findMinAndMax([7]) != (7, 7):
62     print('测试失败!')
63 elif findMinAndMax([7, 1]) != (1, 7):
64     print('测试失败!')
65 elif findMinAndMax([7, 1, 3, 9, 5]) != (1, 9):
66     print('测试失败!')
67 else:
68     print('测试成功!')