﻿ Python: Flatten a given nested list structure - w3resource

# 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: ## 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: ## 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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