Find Rows with given element in Matrix

Given a Matrix, get index of rows with K as elements.

Input : test_list = [[4, 5, 6], [1, 4, 5], [6, 9, 1], [0, 3 ,1]], K = 6
Output : [0, 2]
Explanation : Matrix row number 0 and 2 have 6 as element. 

Input : test_list = [[4, 5, 6], [1, 4, 5], [6, 9, 1], [0, 3 ,1]], K = 4
Output : [0, 1]
Explanation : Matrix row number 0 and 1 have 4 as element.

Method #1 : Using loop
In this, each row is iterated and K is checked in each row using in operator, if element is found, row number is appended in result.

# Python3 code to demonstrate working of
# Sublists with K 
# Using loop

# initializing list
test_list = [[4, 5, 6], [1, 4, 5], [6, 9, 1], [0, 3 ,1]]
             
# printing original list
print("The original list is : " + str(test_list))

# initializing K 
K = 6

res = []

# loop is used for iterating rows
for sub in test_list :
    if K in sub:
        
        # index() computed the row index
        res.append(test_list.index(sub))

# printing result
print("Sublist index with K : " + str(res))

Output

The original list is : [[4, 5, 6], [1, 4, 5], [6, 9, 1], [0, 3, 1]]
Sublist index with K : [0, 2]

Method #2 : Using list comprehension + enumerate()
In this, index of required row is extracted using enumerate(). The list comprehension is used for iteration of rows.

# Python3 code to demonstrate working of
# Sublists with K 
# Using list comprehension + enumerate()

# initializing list
test_list = [[4, 5, 6], [1, 4, 5], [6, 9, 1], [0, 3 ,1]]
             
# printing original list
print("The original list is : " + str(test_list))

# initializing K 
K = 6

# enumerate() is used to get row index
res = [idx for idx, sub in enumerate(test_list) if K in sub]

# printing result
print("Sublist index with K : " + str(res))

Output

The original list is : [[4, 5, 6], [1, 4, 5], [6, 9, 1], [0, 3, 1]]
Sublist index with K : [0, 2]