Python – Rear column in Multi-sized Matrix

Given a Matrix with variable lengths rows, extract last column.

Input : test_list = [[3, 4, 5], [7], [8, 4, 6], [10, 3]]
Output : [5, 7, 6, 3]
Explanation : Last elements of rows filtered.

Input : test_list = [[3, 4, 5], [7], [8, 4, 6]]
Output : [5, 7, 6]
Explanation : Last elements of rows filtered.

Method #1 : Using loop

This is brute way to solve this, we access last element using “-1”, iterate for each row.

Python3

# Python3 code to demonstrate working of
# Rear column in Multisized Matrix
# Using loop

# initializing list
test_list = [[3, 4, 5], [7], [8, 4, 6, 1], [10, 3]]

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

res = []
for sub in test_list:

    # getting rear element using "-1"
    res.append(sub[-1])

# printing results
print("Filtered column : " + str(res))

Output

The original list is : [[3, 4, 5], [7], [8, 4, 6, 1], [10, 3]]
Filtered column : [5, 7, 1, 3]

Method #2 : Using list comprehension

This is another way to solve this, in this, we perform above task in similar way, just as a shorthand. 

Python3

# Python3 code to demonstrate working of
# Rear column in Multisized Matrix
# Using list comprehension

# initializing list
test_list = [[3, 4, 5], [7], [8, 4, 6, 1], [10, 3]]

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

# one-liner to solve this problem
res = [sub[-1] for sub in test_list]

# printing results
print("Filtered column : " + str(res))

Output

The original list is : [[3, 4, 5], [7], [8, 4, 6, 1], [10, 3]]
Filtered column : [5, 7, 1, 3]