Calculating the sum of all columns of a 2D NumPy array

• Last Updated : 02 Sep, 2020

Let us see how to calculate the sum of all the columns of a 2 dimensional NumPy array.

Example :

```Input :
[[1, 2, 3, 4, 5],
[5, 6, 7, 8, 9],
[2, 1, 5, 7, 8],
[2, 9, 3, 1, 0]]

Output :  [10, 18, 18, 20, 22]

Input :
[[5, 4, 1, 7],
[0, 9, 3, 5],
[3, 2, 8, 6]]

Output : [8, 15, 12, 18]
```

Approach 1 : We will be using the `sum()` method. We will pass parameter` axis = 0` to get the sum columns wise.

 `# importing numpy``import` `numpy as np`` ` `# initialize the 2-d array``arr ``=` `np.array([[``1``, ``2``, ``3``, ``4``, ``5``],``                ``[``5``, ``6``, ``7``, ``8``, ``9``],``                ``[``2``, ``1``, ``5``, ``7``, ``8``],``                ``[``2``, ``9``, ``3``, ``1``, ``0``]])`` ` `# calculating column wise sum``sum_2d ``=` `arr.``sum``(axis ``=` `0``)`` ` `# displaying the sum``print``(``"Column wise sum is :\n"``, sum_2d)`

Output :

```Column wise sum is :
[10 18 18 20 22]
```

Approach 2 : We can also use the `numpy.einsum()` method, with parameter `'ij->j'`.

 `# importing numpy``import` `numpy as np`` ` `# initialize the 2-d array``arr ``=` `np.array([[``1``, ``2``, ``3``, ``4``, ``5``],``                ``[``5``, ``6``, ``7``, ``8``, ``9``],``                ``[``2``, ``1``, ``5``, ``7``, ``8``],``                ``[``2``, ``9``, ``3``, ``1``, ``0``]])`` ` `# calculating column wise sum``sum_2d ``=` `np.einsum(``'ij->j'``, arr)`` ` `# displaying the sum``print``(``"Column wise sum is :\n"``, sum_2d)`

Output :

```Column wise sum is :
[10 18 18 20 22]
```

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