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1. Sum of List Elements2. Largest Element in List3. Smallest Element in List4. Count Occurrences in List5. Remove Duplicates from List6. Merge Two Lists7. Intersection of Lists8. Union of Lists9. Sort List10. Reverse List11. Check if List is Sorted12. Find Second Largest Element13. Find N Largest Elements14. Clone / Copy List15. Rotate List16. Remove Empty Lists17. Flatten Nested List18. Find Common Elements of Two Lists19. List Slicing Programs20. Replace List Elements21. Remove Element by Value22. Count Prime Numbers in List23. Pair Sum Problem24. Unique Elements from Both Lists25. List Difference

Flatten Nested List in Python

Flatten a shallow nested list (list of lists) into a single list.

IntermediateList ProgramsExample 17 of 25
flatten-nested-list.py
1# Program to flatten a nested list (one level)
2

3items = eval(input("Enter a nested list (e.g., [[1, 2], [3, 4]]): "))
4

5flattened = [elem for sublist in items for elem in sublist]
6

7print("Flattened list:", flattened)

Output

Enter a nested list (e.g., [[1, 2], [3, 4]]): [[1, 2], [3, 4]]
Flattened list: [1, 2, 3, 4]

What's going on

We use a nested list comprehension to iterate over sublists and their elements.

After this program

If the idea is still fuzzy, read Day 5: Lists and List Methods in the Python course. For a short check, try the Python quiz (300 questions). Stay with all 25 list programs, or see every topic on Python exercises.

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