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Python中的二維列表使用及說明_python

作者：iFulling ? 更新時間： 2023-01-21 編程語言

一、概念

二維列表的元素還是列表（列表的嵌套），稱之為二維列表。

需要通過行標和列標來訪問二維列表的元素

二、創(chuàng)建二維列表

1、追加一維列標來生成二維列標

生成一個4行3列的二維列表

row1 = [3, 4, 5]
row2 = [1, 5, 9]
row3 = [2, 5, 8]
row4 = [7, 8, 9]
matrix = []
matrix.append(row1)
matrix.append(row2)
matrix.append(row3)
matrix.append(row4)
print(matrix)

輸出結(jié)果：

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

2、直接賦值生成二維列表

定義一個3行4列的二維列表

matrix = [[], [], []]
matrix[0] = [3, 4, 5, 6]
matrix[1] = [8, 7, 9, 5]
matrix[2] = [0, 2, 5, 8]
print(matrix)

輸出結(jié)果：

[[3, 4, 5, 6], [8, 7, 9, 5], [0, 2, 5, 8]]

三、一維列標與二維列表的轉(zhuǎn)換

1、一維列表轉(zhuǎn)換成二維列表

將1到24的全部數(shù)字按順序放到一個4行6列的二維列表里

# 將1到24的全部數(shù)字按順序放到一個4行6列的二維列表里
nums = []
for i in range(1, 25):
? ? nums.append(i)

martix = []
for k in range(4):
? ? row = []
? ? for j in range(1, 7):
? ? ? ? row.append(j + 6 * k)
? ? martix.append(row)

for arr in martix:
? ? print(arr)

輸出結(jié)果：

[1, 2, 3, 4, 5, 6]
[7, 8, 9, 10, 11, 12]
[13, 14, 15, 16, 17, 18]
[19, 20, 21, 22, 23, 24]

2、二維列表轉(zhuǎn)換成一維列表

將一個3行5列的二維列表扁平化一維列表

# 將一個3行5列的二維列表扁平化一維列表
nums = [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15]]
arr = []
for i in nums:
? ? for j in i:
? ? ? ? arr.append(j)
print(arr)

輸出結(jié)果：

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

3、利用NumPy實現(xiàn)數(shù)組的變維操作

利用NumPy數(shù)組提供的 reshape(m, n) 實現(xiàn)數(shù)組的變維

（1）一維數(shù)組變成二維數(shù)組

In [31]:import numpy as np

In [32]:arr1 = np.arange(1,25) ?# arange() 創(chuàng)建一個等差數(shù)組

In [33]:arr2 = arr1.reshape(4, 6) ?# reshape（）一維轉(zhuǎn)二維

In [34]:arr2
Out[34]:?
array([[ 1, ?2, ?3, ?4, ?5, ?6],
? ? ? ?[ 7, ?8, ?9, 10, 11, 12],
? ? ? ?[13, 14, 15, 16, 17, 18],
? ? ? ?[19, 20, 21, 22, 23, 24]])

In [35]:arr2 = arr1.reshape(3, 8)

In [36]:arr2
Out[36]:?
array([[ 1, ?2, ?3, ?4, ?5, ?6, ?7, ?8],
? ? ? ?[ 9, 10, 11, 12, 13, 14, 15, 16],
? ? ? ?[17, 18, 19, 20, 21, 22, 23, 24]])?

（2）二維數(shù)組轉(zhuǎn)換成一維數(shù)組

In [36]:arr2
Out[36]:?
array([[ 1, ?2, ?3, ?4, ?5, ?6, ?7, ?8],
? ? ? ?[ 9, 10, 11, 12, 13, 14, 15, 16],
? ? ? ?[17, 18, 19, 20, 21, 22, 23, 24]])

In [37]:arr1 = arr2.reshape(1, 24)[0]

In [38]:arr1
Out[38]:?
array([ 1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24])

四、訪問二維列表

通過行標與列標來訪問二維列表（可以通過切片運算訪問行）

1、訪問行

In [36]:arr2
Out[36]:?
array([[ 1, ?2, ?3, ?4, ?5, ?6, ?7, ?8],
? ? ? ?[ 9, 10, 11, 12, 13, 14, 15, 16],
? ? ? ?[17, 18, 19, 20, 21, 22, 23, 24]])

In [39]:arr2[1]
Out[39]: array([ 9, 10, 11, 12, 13, 14, 15, 16])

2、訪問元素

In [40]:arr2
Out[40]:?
array([[ 1, ?2, ?3, ?4, ?5, ?6, ?7, ?8],
? ? ? ?[ 9, 10, 11, 12, 13, 14, 15, 16],
? ? ? ?[17, 18, 19, 20, 21, 22, 23, 24]])

In [41]:arr2[1][2] ?# 第2行第3列
Out[41]: 11

3、NumPy二維數(shù)組的訪問

In [42]:import numpy as np

In [43]:arr2
Out[43]:?
array([[ 1, ?2, ?3, ?4, ?5, ?6, ?7, ?8],
? ? ? ?[ 9, 10, 11, 12, 13, 14, 15, 16],
? ? ? ?[17, 18, 19, 20, 21, 22, 23, 24]])

In [44]:arr2[1] ?# 訪問行
Out[44]: array([ 9, 10, 11, 12, 13, 14, 15, 16])

In [45]:arr2[:, 0] ?# 訪問列
Out[45]: array([ 1, ?9, 17])

In [46]:arr2[2, 3] ?# 訪問元素
Out[46]: 20

總結(jié)

原文鏈接：https://blog.csdn.net/realoser/article/details/122154362

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