Question

我试图创建两个列表a和b。

和a和b应满足这些条件：

len(a) == len(b) == 5
a == b
a is not b
a[0] is b[0]
a[1] is not b[1]
a[2] is b[2]
a[3] is not b[3]
a[4] is b[4]

我尝试使用

b = copy.deepcopy(a)

但它没有通过

a[1] is not b[1]
and
a[3] is not b[3]

有人可以帮我吗？

Answer 1

以下是一种可行的方法：

a = [0, [1], 2, [3], 4]

b = copy.deepcopy(a)

这可行，因为deepcopy会插入：

对于不可变对象（如int或str），对同一对象的引用，（共享相等 和< / strong> 身份）;或

对于可变对象（如list），对对象（深层）副本的引用（共享相等 但不是 身份）;

进入新对象。

演示：

>>> from copy import deepcopy >>> a = [0, [1], 2, [3], 4] >>> b = deepcopy(a) >>> print a == b, a is b True False >>> for a_i, b_i in zip(a, b): print a_i == b_i, a_i is b_i True True True False True True True False True True

Answer 2

这可能不是您正在寻找的答案，但至少它会帮助您理解这个概念。值相同，但索引1和3中的元素因参考而不同。希望这会有所帮助。

import copy

avalues = [(1,1),(2,4),(3,9),(4,16),(5,25)]
bvalues = [(1,1),(2,4),(3,9),(4,16),(5,25)]
a = [avalues[0],avalues[1],avalues[2],avalues[3],avalues[4]]
b = [avalues[0],bvalues[1],avalues[2],bvalues[3],avalues[4]]

print "len(a) == 5:", len(a) == 5
print "len(a) == len(b):", len(a) == len(b)
print "a == b:", a == b
print "a is not b:", a is not b
print "a[0] is b[0]:", a[0] is b[0]
print "a[1] is not b[1]:", a[1] is not b[1]
print "a[2] is b[2]:", a[2] is b[2]
print "a[3] is not b[3]:", a[3] is not b[3]
print "a[4] is b[4]:", a[4] is b[4]

Python复制包含引用副本和值副本的列表

2 个答案: