# Python Define a Two-Dimensional Array or Matrix

> Create a 2D array in Python using numpy.zeros for matrix operations, or a nested list comprehension if you want to avoid the numpy dependency

**URL:** https://sentry.io/answers/define-a-two-dimensional-array-in-python/

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## The Problem

How can I create an empty two-dimensional array in Python, e.g. for matrix operations?

## The Solution

The best way to create two-dimensional (2D) arrays or matrices is by using Python's `numpy` module, which provides comprehensive and performant functionality for manipulating multidimensional arrays. We can create a 2D array by passing a tuple to the [`zeros`](https://numpy.org/doc/stable/reference/generated/numpy.zeros.html#numpy.zeros) function. The following code will create a 3-by-3 2D array with all values set to zero:

```python
import numpy

matrix = numpy.zeros((3,3))

# array([[0., 0., 0.],
#        [0., 0., 0.],
#        [0., 0., 0.]])
```

Note that [`numpy.matrix`](https://numpy.org/doc/stable/reference/generated/numpy.matrix.html) is deprecated and should not be used for this operation.

To create a 2D array without using `numpy`, we can initialize a list of lists using a list comprehension. This will be slower and deprive us of the use of `numpy`'s matrix operations, but may be desirable in cases where we don't want to add the dependency. We can use code similar to the following:

```python
matrix = [[0 for x in range(3)] for y in range(3)] # x = width, y = height
# [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
```

In both of these structures, we can read and write individual elements with the following syntax:

```python
matrix[0][0] = 1 # set top-left corner to 1

print(matrix[2][2]) # print value of bottom-right corner
```

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*Source: [sentry.io/answers/define-a-two-dimensional-array-in-python/](https://sentry.io/answers/define-a-two-dimensional-array-in-python/)*