List is a common type of data structure in Python. While we have used the list and 2d list, the use of 3d list is increasing day by day, mostly in case of web development.
Given a 3D list, the task is to convert it into a 2D list. These type of problems are encountered while working on projects or while contributing to open source.
Below are some ways to achieve the above task.

Input:
[[[3], [4]], [[5], [6]], [[7], [8]]]
Output:
[[3], [4], [5], [6], [7], [8]]

Method #1: Using simple iteration to convert a 3D list into a 2D list.

# Python code to convert a 3D list into a 2D list

# Input list initialization
Input = [[[3], [4]], [[5], [6]], [[7], [8]]]

# Output list initialization
Output = []

# Using iteration
for temp in Input:
	for elem in temp:
		Output.append(elem)

# printing output
print("Initial 3d list is")
print(Input)
print("Converted 2d list is")
print(Output)

Output:

Initial 3d list is
[[[3], [4]], [[5], [6]], [[7], [8]]]
Converted 2d list is
[[3], [4], [5], [6], [7], [8]]

Method #2: Using List Comprehension to convert a 3D list into a 2D list

# Python code to convert a 3D list into a 2D list

# Input list initialization
Input = [[[1, 1], [2, 7]], [[3], [4]], [[6, 5], [6]]]

# Using list comprehension
Output = [elem for twod in Input for elem in twod]

# printing output
print("Initial 3d list is")
print(Input)
print("Converted 2d list is")
print(Output)

Output:

Initial 3d list is
[[[1, 1], [2, 7]], [[3], [4]], [[6, 5], [6]]]
Converted 2d list is
[[1, 1], [2, 7], [3], [4], [6, 5], [6]]