# Python – Summation Matrix columns

• Last Updated : 30 Dec, 2020

Sometimes, we are encountered with such problem in which we need to find the sum of each column in a matrix i.e sum of each index in list of lists. This kind of problem is quite common and useful in competitive programming. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using `sum() + list comprehension + zip()`
The combination of above methods are required to solve this particular problem. The sum function is used to get the required sum value and zip function provides the combination of like indices and then list is created using list comprehension.

 `# Python3 code to demonstrate``# Summation of each column in Matrix``# using sum() + list comprehension + zip()`` ` `# initializing list``test_list ``=` `[[``3``, ``7``, ``6``], [``1``, ``3``, ``5``], [``9``, ``3``, ``2``]]`` ` `# printing original list``print``(``"The original list : "` `+` `str``(test_list))`` ` `# using sum() + list comprehension + zip()``# Summation of each column in Matrix``res ``=` `[``sum``(idx) ``for` `idx ``in` `zip``(``*``test_list)]`` ` `# print result``print``(``"The Summation of each index list is : "` `+` `str``(res))`

Output :

```The original list : [[3, 7, 6], [1, 3, 5], [9, 3, 2]]
The Summation of each index list is : [13, 13, 13]
```

Method #2 : Using `map() + sum() + zip()`
This works in almost similar way as the above method, but the difference is just that we use map function to build the sum list rather than using list comprehension.

 `# Python3 code to demonstrate``# Summation of each column in Matrix``# using map() + sum() + zip()`` ` `# initializing list``test_list ``=` `[[``3``, ``7``, ``6``], [``1``, ``3``, ``5``], [``9``, ``3``, ``2``]]`` ` `# printing original list``print``(``"The original list : "` `+` `str``(test_list))`` ` `# using map() + sum() + zip()``# Summation of each column in Matrix``res ``=` `list``(``map``(``sum``, ``zip``(``*``test_list)))`` ` `# print result``print``(``"The Summation of each index list is : "` `+` `str``(res))`

Output :

```The original list : [[3, 7, 6], [1, 3, 5], [9, 3, 2]]
The Summation of each index list is : [13, 13, 13]
```

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