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Python: Flatten a given nested list structure

Python List: Exercise - 72 with Solution

Write a Python program to flatten a given nested list structure.

Sample Solution-1:

Python Code:

def flatten_list(n_list):
    result_list = []
    if not n_list: return result_list
    stack = [list(n_list)]
    while stack:
        c_num = stack.pop()
        next = c_num.pop()
        if c_num: stack.append(c_num)
        if isinstance(next, list):
            if next: stack.append(list(next))
        else: result_list.append(next)
    result_list.reverse()
    return result_list 
n_list = [0, 10, [20, 30], 40, 50, [60, 70, 80], [90, 100, 110, 120]]
print("Original list:") 
print(n_list)
print("\nFlatten list:")
print(flatten_list(n_list))

Sample Output:

Original list:
[0, 10, [20, 30], 40, 50, [60, 70, 80], [90, 100, 110, 120]]

Flatten list:
[0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120]

Flowchart:

Flowchart: Flatten a given nested list structure.

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:


Sample Solution-2:

Loop over elements, use list.extend() if the element is a list, list.append() otherwise.

Python Code:

def flatten_list(nums):
  result = []
  for i in nums:
    result.extend(i) if isinstance(i, list) else result.append(i)
  return result     
n_list = [0, 10, [20, 30], 40, 50, [60, 70, 80], [90, 100, 110, 120]]
print("Original list:") 
print(n_list)
print("\nFlatten list:")
print(flatten_list(n_list))

Sample Output:

Original list:
[0, 10, [20, 30], 40, 50, [60, 70, 80], [90, 100, 110, 120]]

Flatten list:
[0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120]

Flowchart:

Flowchart: Flatten a given nested list structure.

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:


Python Code Editor:

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Next: Write a Python program to remove consecutive (following each other continuously) duplicates (elements) of a given list.

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Python: Tips of the Day

Creates a list of elements, grouped based on the position in the original lists:

Example:

def tips_zip(*args, fill_value=None):
  	max_length = max([len(lst) for lst in args])
 	 result = []
  	for i in range(max_length):
   	 result.append([
      args[k][i] if i < len(args[k]) else fillvalue for k in range(len(args))
   	 ])
 	 return result
print(tips_zip(['a', 'b'], [1, 2], [True, False]))
print(tips_zip(['a'], [1, 2], [True, False]))
print(tips_zip(['a'], [1, 2], [True, False], fill_value = '1'))

Output:

[['a', 1, True], ['b', 2, False]]
[['a', 1, True], [None, 2, False]]
[['a', 1, True], ['1', 2, False]]