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Python Program that filters out non-empty rows of a matrix

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  • Last Updated : 26 Oct, 2022
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Given Matrix, the following article shows how to filter all the Non-Empty rows of a matrix. In simpler terms, the codes provided below return a matrix after removing empty rows from it. 

Input : test_list = [[4, 5, 6, 7], [], [], [9, 8, 1], []] 
Output : [[4, 5, 6, 7], [9, 8, 1]] 
Explanation : All empty rows are removed.
Input : test_list = [[4, 5, 6, 7], [], [9, 8, 1], []] 
Output : [[4, 5, 6, 7], [9, 8, 1]] 
Explanation : All empty rows are removed. 

Method 1: Using list comprehension and len()

In this we check each row for its length, if its length is greater than 0 then that row is added to result.

Python3




# initializing list
test_list = [[4, 5, 6, 7], [], [], [9, 8, 1], []]
 
# printing original lists
print("The original list is : " + str(test_list))
 
# checking for row lengths using len()
res = [row for row in test_list if len(row) > 0]
 
# printing result
print("Filtered Matrix " + str(res))

Output

The original list is : [[4, 5, 6, 7], [], [], [9, 8, 1], []]
Filtered Matrix [[4, 5, 6, 7], [9, 8, 1]]

Method 2 : Using filter(), lambda and len()

In this, we filter rows w.r.t lengths using filter() and lambda function. The len() is used to get the length.

Python3




# initializing list
test_list = [[4, 5, 6, 7], [], [], [9, 8, 1], []]
 
# printing original lists
print("The original list is : " + str(test_list))
 
# checking for row lengths using len()
# filtering using filter() + lambda
res = list(filter(lambda row: len(row) > 0, test_list))
 
# printing result
print("Filtered Matrix " + str(res))

 Output:

The original list is : [[4, 5, 6, 7], [], [], [9, 8, 1], []]

Filtered Matrix [[4, 5, 6, 7], [9, 8, 1]]

Method 3 : Using find() method

Python3




#Filter non empty rows
# initializing list
test_list = [[4, 5, 6, 7], [], [], [9, 8, 1], []]
 
# printing original lists
print("The original list is : " + str(test_list))
res=[]
for i in test_list:
    if str(i).find("[]")==-1:
        res.append(i)
 
# printing result
print("Filtered Matrix " + str(res))

Output

The original list is : [[4, 5, 6, 7], [], [], [9, 8, 1], []]
Filtered Matrix [[4, 5, 6, 7], [9, 8, 1]]

Method 4 : Using remove() method
 

Python3




#Python Program that filters out non-empty rows of a matrix
# initializing list
test_list = [[4, 5, 6, 7], [], [], [9, 8, 1], []]
 
# printing original lists
print("The original list is : " + str(test_list))
 
while([] in test_list):
    test_list.remove([])
# printing result
print("Filtered Matrix " + str(test_list))

Output

The original list is : [[4, 5, 6, 7], [], [], [9, 8, 1], []]
Filtered Matrix [[4, 5, 6, 7], [9, 8, 1]]

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