当您有一个多级列表[python]时，该列表中的引用点是如何变化的？

例如，你有：

a = [1,2]

b = [a,3]

c = b[:]

a[0] = 7

b[1] = 8

print c

你得到了

[[7,2,3]

---

为什么

3

没有改为

8

？

正如其他人提到的，基本原则是，当你分配

c

时，你是在做一个“浅拷贝”

要详细说明，您有以下几点：

a = [1,2]
# a = list(1,2) at address AAA

b = [a, 3]
# b = list( [REFERENCE to AAA], 3) at address BBB

c = b[:]
# c = NEW list( b[0], b[1] ) at address CCC
# c = list( [REFERENCE to AAA], 3) at address CCC

a[0] = 7
# change item at AAA, offset [0], to 7
# 'b' points to AAA, so it will see change
# 'c' points to AAA, so it will see change

b[1] = 8
# change item at BBB, offset [1], to 8
# 'a' doesn't know about this, so it doesn't care.
# 'c' doesn't point to BBB, so it doesn't see the change.

print c
# Prints CCC offset [0], which refers to the AAA list, as changed,
# then prints CCC offset [1], which is still 3.