5. 列表转置

>>> a = [[1,2,3],[4,5,6],[7,8,9]]
>>> list(map(list, zip(*a)))
[[1, 4, 7], [2, 5, 8], [3, 6, 9]]

Python 列表常用方法

1. 建立列表

• 直接建立

>>> [0, 1, 2, 3, 4]
[0, 1, 2, 3, 4]

• 函数 / 方法 / 产生器建立

>>> [i for i in range(5)]
[0, 1, 2, 3, 4]

• 一维双变量交互建立

>>> [(i, j*10) for i in range(5) for j in range(5)]
[(0, 0), (0, 10), (0, 20), (0, 30), (0, 40), (1, 0), (1, 10), (1, 20), ( 1, 30), (1, 40), (2, 0), (2, 10), (2, 20), (2, 30), (2, 40), (3, 0), (3, 10), (3, 20), (3, 30), (3, 40), (4, 0), (4, 10), (4, 20), (4, 30), (4, 40) ]

• 一维双变量对应建立

>>> [(i, j*10) for i, j in zip(range(5), range(5))]
[(0, 0), (1, 10), (2, 20), (3, 30), (4, 40)]

• 多维列表建立

>>> [[[i, j] for i in range(5)] for j in range(5)]
[[[0, 0], [1, 0], [2, 0], [3, 0], [4, 0]],
 [[0, 1], [1, 1], [2, 1], [3, 1], [4, 1]],
 [[0, 2], [1, 2], [2, 2], [3, 2], [4, 2]],
 [[0, 3], [1, 3], [2, 3], [3, 3], [4, 3]],
 [[0, 4], [1, 4], [2, 4], [3, 4], [4, 4]]]

• 从其他变量建立

>>> list('We are the world')
['W', 'e', ' ', 'a', 'r', 'e', ' ', 't', 'h', 'e', ' ', 'w', 'o', 'r', 'l', 'd']
>>> list(range(5))
[0, 1, 2, 3, 4]

2. 修改列表

• 单一元素修改

>>> a = [1, 2, 3, 5]
>>> a[3] = 4
>>> a
[1, 2, 3, 4]

• 部份修改

>>> a[1:3] = [5, 6]
[1, 5, 6, 4]
>>> a[1:3] = [8]
[1, 8, 4]

3. 复制列表

• 记忆体参考位置复制

>>> a = [1, 2, 3, 4]
>>> b = a
>>> b[1] = 10
>>> a, b
([1, 10, 3, 4], [1, 10, 3, 4])

• 一维浅层复制

>>> from copy import copy, deepcopy
>>> a = [[1,2,3], [4, 5,6]]
>>> b = copy(a) # 同 b = a[:]
>>> b[