Python: Third largest number from a list of numbers using set

Last update on April 21 2025 13:04:03 (UTC/GMT +8 hours)

29. Find Third Largest Number Using a Set

Write a Python program to find the third largest number from a given list of numbers.Use the Python set data type.

Sample Solution:

Python Code:

# Define a function 'third_largest' that takes a list of 'nums' as input.
def third_largest(nums):
    # Convert the 'nums' list into a set to remove duplicates.
    nums = set(nums)
    
    # Check if the length of 'nums' is less than 3. If so, return None since it doesn't have a third largest element.
    if len(nums) < 3:
        return None
    
    # Convert the 'nums' set back into a list and sort it in reverse order (largest to smallest).
    nums = list(nums)
    nums.sort(reverse=True)
    
    # Return the third element in the sorted list, which is the third largest number.
    return nums[2]

# Define a list of numbers 'nums' for testing.
nums = [1, 2, 3, 4, 5, 6, 7, 8, 9]
print("Original list of numbers:")
print(nums)

# Call the 'third_largest' function and print the third largest number for the given list.
print("Third largest number of the said list of numbers:")
print(third_largest(nums))

# Repeat the process for different input lists.
nums = [1, 2, 3, 4, 5, 5, 6, 7, 7, 8, 8, 9, 10]
print("\nOriginal list of numbers:")
print(nums)
print("Third largest number of the said list of numbers:")
print(third_largest(nums))

nums = [1, 2, 3]
print("\nOriginal list of numbers:")
print(nums)
print("Third largest number of the said list of numbers:")
print(third_largest(nums))

nums = [1, 2, 2]
print("\nOriginal list of numbers:")
print(nums)
print("Third largest number of the said list of numbers:")
print(third_largest(nums))

nums = [1, 2]
print("\nOriginal list of numbers:")
print(nums)
print("Third largest number of the said list of numbers:")
print(third_largest(nums))

Sample Output:

Original list of numbers:
[1, 2, 3, 4, 5, 6, 7, 8, 9]
Third largest number of the said list of numbers:
7
Original list of numbers:
[1, 2, 3, 4, 5, 5, 6, 7, 7, 8, 8, 9, 10]
Third largest number of the said list of numbers:
8
Original list of numbers:
[1, 2, 3]
Third largest number of the said list of numbers:
1
Original list of numbers:
[1, 2, 2]
Third largest number of the said list of numbers:
None
Original list of numbers:
[1, 2]
Third largest number of the said list of numbers:
None

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to convert a list to a set to remove duplicates and then find the third largest number.
Write a Python program to sort the unique elements of a list and extract the third largest value using negative indexing.
Write a Python program to use heapq.nlargest on a set derived from a list to get the third largest number.
Write a Python program to implement a function that returns the third largest unique element from a list, or an error if not enough elements exist.

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