Python中将三维列表转换为二维列表的方法

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Python是一种广泛使用的编程语言，用于各种目的，例如Web开发、数据科学、机器学习以及执行不同的自动化操作。在本文中，我们将学习将三维列表转换为二维列表的不同方法。

让我们首先看看这两种类型的列表是什么样的：

三维列表

Three_dimensional_list = [
   [['Sam', 'Tom'], ['Miller', 'David']],
   [['Rocky', 'Tyler'], ['Mason', 'Petrick']],
   [['Stefen', 'Damon'], ['Matt', 'Jeremy']]
] # This is the basic structure of a three dimensional list

二维列表

Two_dimensional_list = [
   ['Sam', 'Tom'],
   ['Miller', 'David'],
   ['Rocky', 'Tyler'],
   ['Mason', 'Petrick'],
   ['Stefen', 'Damon'],
   ['Matt', 'Jeremy']
] # This is the basic structure of a two Dimensional list

将三维列表转换为二维列表的不同方法

嵌套循环

这是将三维列表转换为二维列表最快的方法。我们将简单地检查列表中的每个元素，并将其展平成二维列表。让我们来看一个例子，以便更好地理解：

示例

def convert_list_to_2D(main_list): # The 3 dimensional list is given as input to the function convert_list_to_2D
   final_list = [] # An empty list is created to store all the 2 dimension list elements
   for sublist in main_list: # For loop is used to check each element in the sublists in the 3D list 
      for subsublist in sublist: # Second for loop to chek each element in the sublists of sublists of the 3D list
         final_list.append(subsublist) # All the sublists are moved to the final new list created
   return final_list

Three_dimensional_list = [
   [['Sam', 'Tom'], ['Miller', 'David']],
   [['Rocky', 'Tyler'], ['Mason', 'Petrick']],
   [['Stefen', 'Damon'], ['Matt', 'Jeremy']]
] # The 3D list is given as input

Two_dimensional_list = convert_list_to_2D(Three_dimensional_list) # The function convert_list_to_2D is run
print(Two_dimensional_list)

输出

上述示例的输出如下：

[['Sam', 'Tom'], ['Miller', 'David'], ['Rocky', 'Tyler'], ['Mason', 
'Petrick'], ['Stefen', 'Damon'], ['Matt', 'Jeremy']] # The 3D list is 
converted into 2D list

列表推导式

这是一种非常有效的方法，可以检查给定输入列表中存在的每个元素。让我们来看一个例子，以便更好地理解：

示例

def convert_list_to_2D(main_list): # The 3 dimensional list is given as input to the function convert_list_to_2D
   return [subsublist for sublist in main_list for subsublist in sublist] # We will use for loop to check each element in sublist and sublist of sublist and convert them into a 2D list

Three_dimensional_list = [
   [['Sam', 'Tom'], ['Miller', 'David']],
   [['Rocky', 'Tyler'], ['Mason', 'Petrick']],
   [['Stefen', 'Damon'], ['Matt', 'Jeremy']]
] # The 3D list is given as input

Two_dimensional_list = convert_list_to_2D(Three_dimensional_list) # The function convert_list_to_2D is run
print(Two_dimensional_list)

# Note: This method is more preferable because it is a compact method and less lines of codes are required

输出

上述示例的输出如下：

[['Sam', 'Tom'], ['Miller', 'David'], ['Rocky', 'Tyler'], ['Mason', 
'Petrick'], ['Stefen', 'Damon'], ['Matt', 'Jeremy']] # The 3D list is 
converted into 2D list

NumPy库

当列表中的输入数据为数值形式时，此方法最为有用。让我们来看一个例子，以便更好地理解：

示例

import numpy as np # Do not forget to import numpy or else error might occur
def convert_list_to_2D(main_list): # The 3 dimensional list is given as input to the function convert_list_to_2D
   flattened = np.array(main_list).reshape(-1, len(main_list[0][0])) # With the help of np.array we will convert the input list into an array and with the help of reshape, we reshape the array into 2D form
   return flattened.tolist() # The 2D form of array will be converted back into list with the help of tolist function

Three_dimensional_list = [
   [[14, 28], [33, 47]],
   [[59, 36], [71, 18]],
   [[96, 13], [81, 32]]
] # The list is given as input

Two_dimensional_list = convert_list_to_2D(Three_dimensional_list) # The function convert_list_to_2D is run
print(Two_dimensional_list)

输出

上述示例的输出如下：

[[14, 28], [33, 47], [59, 36], [71, 18], [96, 13], [81, 32]] # The 3D list is 
converted into 2D list

手动迭代

在此方法中，我们将手动检查给定输入列表中的每个元素。让我们来看一个例子，以便更好地理解：

示例

def convert_list_to_2D(main_list): # The 3 dimensional list is given as input to the function convert_list_to_2D
# We will first calculate the dimensions of the 2D List
   rows = len(main_list) * len(main_list[0]) # # The number of rows in 2D list will be decide by product of number of sublist in 3D list with the number of sublists in each sublists
   cols = len(main_list[0][0])
   output_list = [[0 for _ in range(cols)] for _ in range(rows)] # A new list to store elements is created and for loop is used to check each element in the list given as input
   
   for i in range(len(main_list)):
      for j in range(len(main_list[i])):
         for k in range(len(main_list[i][j])):
            output_list[i * len(main_list[i]) + j][k] = main_list[i][j][k] 
# Proper values are assigned different positions in the new list created
   
   return output_list

Three_dimensional_list = [
   [['Sam', 'Tom'], ['Miller', 'David']],
   [['Rocky', 'Tyler'], ['Mason', 'Petrick']],
   [['Stefen', 'Damon'], ['Matt', 'Jeremy']]
] # The 3D list is given as input

Two_dimensional_list = convert_list_to_2D(Three_dimensional_list) # The function convert_list_to_2D is run
print(Two_dimensional_list)

输出

上述示例的输出如下：

[['Sam', 'Tom'], ['Miller', 'David'], ['Rocky', 'Tyler'], ['Mason', 
'Petrick'], ['Stefen', 'Damon'], ['Matt', 'Jeremy']] # The 3D list is 
converted into 2D list

结论

掌握将三维列表转换为二维列表的不同方法对于成为一名高效的程序员非常重要。可以选择上述任何一种方法，具体取决于方便程度和程序的应用领域。