Python Program to Find Largest Number in a List

Finding the largest number in a list is a common task in Python. There are multiple way to do but the simplest way to find the largest in a list is by using Python's built-in max() function:

Using max()

Python provides a built-in max() function that returns the largest item in a list or any iterable. The time complexity of this approach is O(n) as it traverses through all elements of an iterable.

a = [10, 24, 76, 23, 12]

# Max() will return the largest in 'a'
largest = max(a)
print(largest)

76

Explanation: max(a): This function takes the list 'a' as input and returns the largest value.

Now, let's explore other methods to find maximum in a list.

Using a Loop (Native method)

If we want to find the largest number in a list without using any built-in method (i.e. max()) function then can use a loop (for loop).

a = [10, 24, 76, 23, 12]

# Assuming first element is largest.
largest = a[0]

# Iterate through list and find largest
for val in a:
    if val > largest:
      
      	# If current element is greater than largest
    	# update it
        largest = val

print(largest)

76

Using reduce() function from functools

Another method to find the largest number in a list is by using the reduce() function along with a lambda expression.

from functools import reduce

a = [10, 24, 76, 23, 12]

# Find the largest number using reduce
largest = reduce(lambda x, y: x if x > y else y, a)

print(largest)

76

Explanation: reduce(lambda x, y: x if x > y else y, a): The reduce() function takes pairs of elements in the list a and applies the lambda function to return the largest value. The lambda function compares x and y and returns the larger of the two.

Using sort()

The sort() method is one of the quick method to get the largest value from list but this approach has a higher time complexity (O(n log n)) compared to using max() which is O(n) time.

a.sort()
largest = a[-1]

Explanation:

• a.sort(): This sorts the list a in ascending order.
• a[-1]: The largest number is the last element in the sorted list.

Which method to choose?

• Using max(): This is easiest and most recommended way.
• Using a Loop: This method is good if we want to solve manually.
• Using reduce(): An advanced option for those interested in functional programming.
• Using sort(): This method is not recommended here due to its higher time complexity.

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• Elements Maximum till current index in List