Python – Sort Matrix by None frequency

Given a Matrix, sort according to None elements frequency.

Input : test_list = [[None, None, 3, None], [12, 4, 5], [None, 3, 4]] 
Output : [[12, 4, 5], [None, 3, 4], [None, None, 3, None]] 
Explanation : 0, 1, 3 counts of None respectively.

Input : test_list = [[None, None, 3, None], [None, 3, 4]] 
Output : [[12, 4, 5], [None, None, 3, None]] 
Explanation : 0, 3 counts of None respectively. 

Method #1 : Using sort()

In this, we perform sort using sort(), and task of extracting None elements frequency using external function in each row. This performs inplace sorting.

Python3

# Python3 code to demonstrate working of
# Sort Matrix by None frequency
# Using sort()

# external sort function
def get_None_freq(row):

    # getting length of None characters
    return len([ele for ele in row if not ele])

# initializing list
test_list = [[None, None, 4], [None, None, 3, None],
             [12, 4, 5], [None, 3, 4]]

# printing original list
print("The original list is : " + str(test_list))

# sorting using sort()
test_list.sort(key = get_None_freq)

# printing result
print("List after sorting : " + str(test_list))

Output:

The original list is : [[None, None, 4], [None, None, 3, None], [12, 4, 5], [None, 3, 4]]
List after sorting : [[12, 4, 5], [None, 3, 4], [None, None, 4], [None, None, 3, None]]

Method #2 : Using sorted() + lambda

In this, instead of external function, lambda function is used to solve this problem. The sorted()  is used to perform task of sorting.

Python3

# Python3 code to demonstrate working of
# Sort Matrix by None frequency
# Using sorted() + lambda

# initializing list
test_list = [[None, None, 4], [None, None, 3, None],
             [12, 4, 5], [None, 3, 4]]

# printing original list
print("The original list is : " + str(test_list))

# sorting using sorted()
# lambda function for None frequency logic
res = sorted(test_list, key=lambda row: len([ele for ele in row if not ele]))

# printing result
print("List after sorting : " + str(res))

Output:

The original list is : [[None, None, 4], [None, None, 3, None], [12, 4, 5], [None, 3, 4]]
List after sorting : [[12, 4, 5], [None, 3, 4], [None, None, 4], [None, None, 3, None]]