Python - Find maximum length sub-list in a nested list

In Python, we often work with nested lists (lists inside lists), and sometimes we need to find out which sub-list has the most items. In this article, we will explore Various methods to Find the maximum length of a sub-list in a nested list.

Using max() Function with key=len

The simplest and most efficient way to find the longest sub-list is to use the built-in max() function. The max() function helps us find the largest item in a list. By using the key=len argument, we tell Python to compare the lengths of the sub-lists instead of the sub-lists themselves.

a = [[1, 2], [3, 4, 5], [6]]

# Find the longest sub-list
b = max(a, key=len)

print(b)

[3, 4, 5]

Other methods of finding the maximum length sub-list in a nested list are:

Using a Loop

Iterate through the nested list and keep track of the sub-list with the maximum length. This method gives us the flexibility to add more logic or custom conditions if needed.

a = [[1, 2], [3, 4, 5], [6]]

# Initialize variables to track the longest sub-list
b = []
max_length = 0

# Loop through each sub-list in the nested list
for sub_list in a:
    if len(sub_list) > max_length:
        b = sub_list
        max_length = len(sub_list)

print(b)

[3, 4, 5]

Using List Comprehension with zip()

List comprehension is a Python feature that lets us write compact and readable code. Generate a tuple of lengths and corresponding sub-lists, then extract the sub-list with the maximum length.

a = [[1, 2], [3, 4, 5], [6]]

# Use list comprehension to find sub-lists with the maximum length
b = max((sublist for sublist in a), key=len)

print(b)

[3, 4, 5]

Using sorted() with reverse=True

Another method to find the longest sub-list is by sorting the nested list by the length of the sub-lists in descending order. After sorting, the first element will be the longest sub-list.

a = [[1, 2], [3, 4, 5], [6]]

# Sort the list by length of sub-lists in descending order
sorted_lists = sorted(a, key=len, reverse=True)

# first element is the longest sub-list
b = sorted_lists[0]

print(b)

[3, 4, 5]