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Python Program that prints the rows of a given length from a matrix
• Last Updated : 16 Nov, 2020

Given a Matrix, the following articles shows how to extract all the rows with a specified length.

Input : test_list = [[3, 4, 5, 6], [1, 4, 6], , [2, 3, 4, 5, 6], [7, 3, 1]], K = 3
Output : [[1, 4, 6], [7, 3, 1]]
Explanation : Extracted lists have length of 3.
Input : test_list = [[3, 4, 5, 6], [1, 4, 6], , [2, 3, 4, 5, 6], [7, 3, 1]], K = 4
Output : [[3, 4, 5, 6]]
Explanation : Extracted lists have length of 4.

Method 1 : Using list comprehension and len()

In this, we perform the task of getting length using len() and list comprehension does the task of filtering all the rows which have a specified length.

## Python3

 `# initializing list``test_list ``=` `[[``3``, ``4``, ``5``, ``6``], [``1``, ``4``, ``6``], [``2``], [``2``, ``3``, ``4``, ``5``, ``6``], [``7``, ``3``, ``1``]]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing K``K ``=` `3`` ` `# list comprehension is used for extracting K len rows``res ``=` `[sub ``for` `sub ``in` `test_list ``if` `len``(sub) ``=``=` `K]`` ` `# printing result``print``(``"The filtered rows : "` `+` `str``(res))`

Output:

The original list is : [[3, 4, 5, 6], [1, 4, 6], , [2, 3, 4, 5, 6], [7, 3, 1]]

The filtered rows : [[1, 4, 6], [7, 3, 1]]

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

In this, we perform the task of filtering using filter() and lambda. len() is used for finding length of rows.

## Python3

 `# initializing list``test_list ``=` `[[``3``, ``4``, ``5``, ``6``], [``1``, ``4``, ``6``], [``2``], [``2``, ``3``, ``4``, ``5``, ``6``], [``7``, ``3``, ``1``]]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing K``K ``=` `3`` ` `# filter() + lambda to filter out rows of len K``res ``=` `list``(``filter``(``lambda` `sub: ``len``(sub) ``=``=` `K, test_list))`` ` `# printing result``print``(``"The filtered rows : "` `+` `str``(res))`

Output:

The original list is : [[3, 4, 5, 6], [1, 4, 6], , [2, 3, 4, 5, 6], [7, 3, 1]]

The filtered rows : [[1, 4, 6], [7, 3, 1]]

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