# Python – Count the frequency of matrix row length

• Last Updated : 27 Mar, 2021

Given a Matrix, the task is to write a Python program to get the count frequency of its rows lengths.

Input : test_list = [[6, 3, 1], [8, 9], , [10, 12, 7], [4, 11]]

Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. And to begin with your Machine Learning Journey, join the Machine Learning - Basic Level Course

Output : {3: 2, 2: 2, 1: 1}

Explanation : 2 lists of length 3 are present, 2 lists of size 2 and 1 of 1 length is present.

Input : test_list = [[6, 3, 1], [8, 9], [10, 12, 7], [4, 11]]

Output : {3: 2, 2: 2}

Explanation : 2 lists of length 3 are present, 2 lists of size 2.

Method #1 : Using dictionary + loop

In this we check for each row length, if length has occurred in the memorize dictionary, then the result is incremented or if a new size occurs, the element is registered as new.

## Python3

 `# Python3 code to demonstrate working of``# Row lengths counts``# Using dictionary + loop`` ` `# initializing list``test_list ``=` `[[``6``, ``3``, ``1``], [``8``, ``9``], [``2``], ``             ``[``10``, ``12``, ``7``], [``4``, ``11``]]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `res ``=` `dict``()``for` `sub ``in` `test_list:`` ` `    ``# initializing incase of new length``    ``if` `len``(sub) ``not` `in` `res:``        ``res[``len``(sub)] ``=` `1`` ` `    ``# increment in case of length present``    ``else``:``        ``res[``len``(sub)] ``+``=` `1`` ` `# printing result``print``(``"Row length frequencies : "` `+` `str``(res))`

Output:

```The original list is : [[6, 3, 1], [8, 9], , [10, 12, 7], [4, 11]]
Row length frequencies : {3: 2, 2: 2, 1: 1}```

Method #2 : Using Counter() + map() + len()

In this, map() and len() get the lengths of each sublist in the matrix, Counter is used to keep the frequency of each of the lengths.

## Python3

 `# Python3 code to demonstrate working of``# Row lengths counts``# Using Counter() + map() + len()``from` `collections ``import` `Counter`` ` `# initializing list``test_list ``=` `[[``6``, ``3``, ``1``], [``8``, ``9``], [``2``],``             ``[``10``, ``12``, ``7``], [``4``, ``11``]]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Counter gets the frequencies of counts``# map and len gets lengths of sublist``res ``=` `dict``(Counter(``map``(``len``, test_list)))`` ` `# printing result``print``(``"Row length frequencies : "` `+` `str``(res))`

Output:

```The original list is : [[6, 3, 1], [8, 9], , [10, 12, 7], [4, 11]]
Row length frequencies : {3: 2, 2: 2, 1: 1}```

My Personal Notes arrow_drop_up