Python学习笔记——Coursera

 1 ###################################
 2 # Mutation vs. assignment
 3 
 4 
 5 ################
 6 # Look alike, but different
 7 
 8 a = [4, 5, 6]
 9 b = [4, 5, 6]
10 print "Original a and b:", a, b
11 print "Are they same thing?", a is b
12 
13 a[1] = 20
14 print "New a and b:", a, b
15 print
16 
17 ################
18 # Aliased
19 
20 c = [4, 5, 6]
21 d = c
22 print "Original c and d:", c, d
23 print "Are they same thing?", c is d
24 
25 c[1] = 20
26 print "New c and d:", c, d
27 print
28 
29 ################
30 # Copied
31 
32 e = [4, 5, 6]
33 f = list(e)
34 print "Original e and f:", e, f
35 print "Are they same thing?", e is f
36 
37 e[1] = 20
38 print "New e and f:", e, f
39 print
40 
41 
42 ###################################
43 # Interaction with globals
44 
45 
46 a = [4, 5, 6]
47 
48 def mutate_part(x):  #注：这里的a默认为global
49     a[1] = x
50 
51 def assign_whole(x): 
52     a = x
53 
54 def assign_whole_global(x):
55     global a
56     a = x
57 
58 mutate_part(100)
59 print a
60 
61 assign_whole(200)
62 print a
63 
64 assign_whole_global(300)
65 print a