# Python | Column wise sum of nested list

Given a nested list (where sublists are of equal length), write a Python program to find the column-wise sum of the given list and return it in a new list.

Examples:

```Input : [[1, 5, 3],
[2, 7, 8],
[4, 6, 9]]
Output : [7, 18, 20]

Input : [[20, 5],
[2, 54],
[45, 9],
[72, 3]]
Output : [139, 71]
```

Method #1 : zip using list comprehension

We can find sum of each column of the given nested list using `zip `function of python enclosing it within list comprehension.

 `# Python3 program to Column wise sum of nested list ` ` `  `def` `column_sum(lst): ` `     `  `     ``return` `[``sum``(i) ``for` `i ``in` `zip``(``*``lst)] ` `     `  `# Driver code ` `lst ``=` `[[``1``, ``5``, ``3``], [``2``, ``7``, ``8``], [``4``, ``6``, ``9``]] ` `print``(column_sum(lst)) `

Output:

```[7, 18, 20]
```

Method #2 : Using map() method

Another apporach is to use map(). We apply the sum function to each element in a column and find sum of each column accordingly.

 `# Python3 program to Column wise sum of nested list ` ` `  `def` `column_sum(lst): ` `     `  `    ``return` `list``(``map``(``sum``, ``zip``(``*``lst))) ` `     `  `# Driver code ` `lst ``=` `[[``1``, ``5``, ``3``], [``2``, ``7``, ``8``], [``4``, ``6``, ``9``]] ` `print``(column_sum(lst)) `

Output:

```[7, 18, 20]
```

Method #3 : Using numpy.sum()

numpy.sum() function returns the sum of array elements over the specified axis.

 `# Python3 program to Column wise sum of nested list ` `from` `numpy ``import` `array ` ` `  `def` `column_sum(lst): ` `    ``arr ``=` `array(lst) ` `    ``return` `sum``(arr, ``0``).tolist() ` `     `  `# Driver code ` `lst ``=` `[[``1``, ``5``, ``3``], [``2``, ``7``, ``8``], [``4``, ``6``, ``9``]] ` `print``(column_sum(lst)) `

Output:

```[7, 18, 20]
```

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