PYTHON
Flattening a List of Lists (Nested Lists)
Learn how to transform a nested list structure into a single, flat list in Python, a common operation when dealing with varied data sources.
def flatten_list_of_lists(nested_list):
flat_list = []
for sublist in nested_list:
for item in sublist:
flat_list.append(item)
return flat_list
# Using list comprehension (more concise):
def flatten_list_comprehension(nested_list):
return [item for sublist in nested_list for item in sublist]
# Example usage:
matrix = [[1, 2, 3], [4, 5], [6, 7, 8, 9]]
flattened_manual = flatten_list_of_lists(matrix)
print(f"Original nested list: {matrix}")
print(f"Flattened using loops: {flattened_manual}")
flattened_comprehension = flatten_list_comprehension(matrix)
print(f"Flattened using list comprehension: {flattened_comprehension}")
How it works: This snippet shows two common ways to flatten a list of lists (or nested list) into a single, one-dimensional list. The first method uses nested loops, iterating through each sublist and then each item within the sublist to append it to a new flat list. The second method demonstrates a more Pythonic and concise approach using a nested list comprehension, achieving the same result in a single line. Both methods are effective for unwrapping nested data structures.