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# Arrays
In computer programming, an array is a structure for storing and retrieving data. We often talk about an array as if it were a grid in space, with each cell storing one element of the data. For instance, if each element of the data were a number, we might visualize a “one-dimensional” array like a list:
| 1 | 5 | 2 | 0 |
A two-dimensional array would be like a table:
| 1 | 5 | 2 | 0 |
| 8 | 3 | 6 | 1 |
| 1 | 7 | 2 | 9 |
A three-dimensional array would be like a set of tables, perhaps stacked as though they were printed on separate pages.
- From [Numpy documentation](https://numpy.org/doc/2.2/user/absolute_beginners.html)
---
In this tutorial we will be introducing arrays and we will be using the numpy library. Arrays, lists, vectors, matrices, sets - You might've heard of them before, they all store data. In programming, an array is a variable that can hold more than one value at a time. We will be using the Numpy python library to create arrays.
Since we already have installed Numpy previously, we can start using the package.
## Import Numpy
When using packages in python, we need to let it know what package we will be using. This is called importing. To import numpy we need to declare it a the start of a script as follows:
```python
import numpy as np
```
<code> import </code> calls for a library to use, in our case it is Numpy.
<code> as </code> gives the library an alias in your script. It's common convention in Python programming to make the code shorter and more readable. We will be using *np* as it's a standard using in many projects.
# Creating arrays
Now that we have imported the library we can create a one dimensional array or *vector*
```python
x = np.array([1,2,3])
```
To create a *matrix* we can nest the arrays to create a two dimensional array.
```python
matrix = np.array([[1,2,3],[4,5,6],[7,8,9]])
```
*Note: for every array we nest, we get a new dimension in our data structure.*
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