在列表的第 i 个列表中附加值

Question

我有 b 这是一个列表，它还包含 10 个列表，列表的每个索引都包含列表本身。现在，当我尝试在第 i 个列表中附加一些值时，它会将其附加到所有列表中。我不明白为什么？帮助。

代码：

a=[3,5,1,7,2,22,9,8,4,11]
b=[[]]*10
d=10
for i in range(len(a)):         
    b[i].append(a[i])
    print b

输出：

[[3], [3], [3], [3], [3], [3], [3], [3], [3], [3]] [[3, 5], [3, 5], [3, 5], [3, 5], [3, 5], [3, 5], [3, 5], [3, 5], [ 3, 5], [3, 5]] [[3, 5, 1], [3, 5, 1], [3, 5, 1], [3, 5, 1], [3, 5, 1], [3, 5, 1], [ 3, 5, 1], [3, 5, 1], [3, 5, 1], [3, 5, 1]] [[3, 5, 1, 7], [3, 5, 1, 7], [3, 5, 1, 7], [3, 5, 1, 7], [3, 5, 1, 7] , [3, 5, 1, 7], [3, 5, 1, 7], [3, 5, 1, 7], [3, 5, 1, 7], [3, 5, 1, 7] ] [[3, 5, 1, 7, 2], [3, 5, 1, 7, 2], [3, 5, 1, 7, 2], [3, 5, 1, 7, 2], [ 3, 5, 1, 7, 2], [3, 5, 1, 7, 2], [3, 5, 1, 7, 2], [3, 5, 1, 7, 2], [3, 5, 1, 7, 2], [3, 5, 1, 7, 2]] [[3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22], [ 3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22], [3, 5, 1, 7, 2, 22]] [[3, 5, 1, 7, 2, 22, 9], [3, 5, 1, 7, 2, 22, 9], [3, 5, 1, 7, 2, 22, 9], [ 3, 5, 1, 7, 2, 22, 9], [3, 5, 1, 7, 2, 22, 9], [3, 5, 1, 7, 2, 22, 9], [3, 5, 1, 7, 2, 22, 9], [3, 5, 1, 7, 2, 22, 9], [3, 5, 1, 7, 2, 22, 9], [3, 5, 1、7、2、22、9]] [[3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8], [3, 5, 1, 7, 2, 22, 9, 8]] [[3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4] , [3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4], [3, 5, 1, 7, 2, 22, 9, 8, 4] ] [[3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [3, 5, 1, 7, 2, 22, 9, 8, 4, 11], [ 3、5、1、7、2、22、9、8、4、11]]

Answer 1

不要像这篇文章建议的那样初始化为可变对象：Append a new item to a list within a list

相反，将列表重写为：

>>> b=[[] for _ in xrange(10)]
>>> b
[[], [], [], [], [], [], [], [], [], []]
>>> b[0].append(0)
>>> b
[[0], [], [], [], [], [], [], [], [], []]

对于你给出的代码，

a=[3,5,1,7,2,22,9,8,4,11]
b=[[] for _ in xrange(10)]
d=10;
for i in range(len(a)):
    b[i].append(a[i])
    print b

输出：

[[3], [], [], [], [], [], [], [], [], []]
[[3], [5], [], [], [], [], [], [], [], []]
[[3], [5], [1], [], [], [], [], [], [], []]
[[3], [5], [1], [7], [], [], [], [], [], []]
[[3], [5], [1], [7], [2], [], [], [], [], []]
[[3], [5], [1], [7], [2], [22], [], [], [], []]
[[3], [5], [1], [7], [2], [22], [9], [], [], []]
[[3], [5], [1], [7], [2], [22], [9], [8], [], []]
[[3], [5], [1], [7], [2], [22], [9], [8], [4], []]
[[3], [5], [1], [7], [2], [22], [9], [8], [4], [11]]