# Single and Multi-Dimensional Arrays

## **Single-Dimensional Arrays**

A **single-dimensional array** is a linear collection of elements, meaning it has only one row of data. Each element is accessed using a single index.

Think of it like a list of numbers in a straight line:

```python
[10, 20, 30, 40, 50]
```

Each item in this array is accessed using a single index.

<figure><img src="https://115028830-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhF2chp1dcxIJhlOQSKVq%2Fuploads%2FkXcUFMICDvoIsMi1TIdm%2Fimage.png?alt=media&#x26;token=1db9907d-9813-4849-89f6-aeaf9e4f4144" alt=""><figcaption></figcaption></figure>

### **Example Using Array Module**

```python
import array

# Creating a single-dimensional array of integers
numbers = array.array('i', [10, 20, 30, 40, 50])

# Accessing elements using their index
print(numbers[0])  # Output: 10
print(numbers[3])  # Output: 40
```

## **Multi-Dimensional Arrays**

A **multi-dimensional array** is an array containing other arrays inside it. The most common type is a **2D array**, which resembles a table with rows and columns.

For example, a **2D array** can be visualised as:

```python
[
  [1, 2, 3], 
  [4, 5, 6], 
  [7, 8, 9]
]
```

Each element is accessed using two indices: one for the row and one for the column.

<figure><img src="https://115028830-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhF2chp1dcxIJhlOQSKVq%2Fuploads%2FCA4mUVb5TAQLL5PT1djI%2Fimage.png?alt=media&#x26;token=74bbfc72-4360-47ae-acf5-20d8d4543369" alt=""><figcaption><p>2D Multidimensional Array</p></figcaption></figure>

### **Example Using NumPy Module**

Python’s built-in `array` module only supports **single-dimensional arrays**, so we use **NumPy** for multi-dimensional arrays.

```python
import numpy as np

# Creating a 2D array (3 rows, 3 columns)
matrix = np.array([
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
])

# Accessing elements using row and column indices
print(matrix[0][1])  # Output: 2 (row 0, column 1)
print(matrix[2][2])  # Output: 9 (row 2, column 2)
```

***

## **Key Differences**

| Feature       | Single-Dimensional Array        | Multi-Dimensional Array                   |
| ------------- | ------------------------------- | ----------------------------------------- |
| **Structure** | A single row of elements        | A grid (rows and columns)                 |
| **Indexing**  | Uses one index (e.g., `arr[2]`) | Uses multiple indices (e.g., `arr[1][2]`) |
| **Usage**     | Used for simple lists of data   | Used for tables, matrices, images, etc.   |
| **Library**   | Can use `array` module or lists | Requires `numpy` for efficient handling   |