**Course Title:** Modern Python Programming: Best Practices and Trends **Section Title:** Data Science and Visualization with Python **Topic:** Introduction to NumPy for numerical computing. ## Overview of NumPy NumPy (Numerical Python) is a library used for efficient numerical computation in Python. It provides support for large, multi-dimensional arrays and matrices, along with a wide range of high-performance mathematical functions to manipulate them. ## Key Features of NumPy - **Arrays**: NumPy arrays are the core data structure used for numerical computations. They provide a way to represent and manipulate multi-dimensional data in a compact and efficient manner. - **Vectorized Operations**: NumPy provides a variety of vectorized operations that allow you to perform mathematical operations on entire arrays at once, making it faster than working with Python lists. - **Linear Algebra**: NumPy comes with a built-in library for linear algebra operations, which includes matrix multiplication, matrix decomposition, and solving systems of linear equations. - **Random Number Generation**: NumPy also includes a module for generating random numbers, which is useful for tasks like data generation and simulation. ## Installing and Importing NumPy To install NumPy, you can use pip: ```bash pip install numpy ``` Once installed, you can import NumPy in your Python code: ```python import numpy as np ``` **Note:** It's a common convention to import NumPy with the alias `np`. ## Basic NumPy Data Types - **ndarray**: The main data structure in NumPy, a multi-dimensional array of elements of the same type. - **dtype**: A data type object that describes the type of elements in a NumPy array. ## Creating NumPy Arrays There are several ways to create a NumPy array: - **Using the `numpy.array()` function**: ```python import numpy as np arr = np.array([1, 2, 3, 4, 5]) print(arr) # Output: [1 2 3 4 5] ``` - **Using the `numpy.arange()` function**: ```python import numpy as np arr = np.arange(5) print(arr) # Output: [0 1 2 3 4] ``` - **Using the `numpy.zeros()` and `numpy.ones()` functions**: ```python import numpy as np arr = np.zeros(5) print(arr) # Output: [0. 0. 0. 0. 0.] arr = np.ones(5) print(arr) # Output: [1. 1. 1. 1. 1.] ``` ## Basic Operations with NumPy Arrays - **Indexing**: Accessing individual elements or a subset of an array. - **Array operations**: Perform operations like addition, subtraction, multiplication, and division on entire arrays. - **Matrix multiplication**: Multiply two arrays together. **Example of Basic Operations:** ```python import numpy as np arr = np.array([1, 2, 3, 4, 5]) print(arr * 2) # Output: [2 4 6 8 10] arr2 = np.array([[1, 2], [3, 4]]) arr3 = np.array([[5, 6], [7, 8]]) # Matrix multiplication print(np.matmul(arr2, arr3)) # Output: [[19 22], [43 50]] ``` ## Common NumPy Functions - **min**, **max**: Compute the minimum or maximum value in an array. - **mean**, **median**: Compute the mean or median of an array. - **sort**: Sort the elements of an array. **Example of Common NumPy Functions:** ```python import numpy as np arr = np.array([3, 1, 4, 2, 5]) # Compute min and max print(np.min(arr)) # Output: 1 print(np.max(arr)) # Output: 5 # Compute mean and median print(np.mean(arr)) # Output: 3.0 print(np.median(arr)) # Output: 3.0 ``` ## Best Practices - **Use NumPy arrays instead of Python lists** for numerical computations. - **Use vectorized operations** instead of iterating over individual elements. - **Use the `numpy.loadtxt()` function** to load numerical data from text files. ## Conclusion In this topic, we've introduced the basics of NumPy, covering its key features, installing and importing NumPy, basic data types, creating NumPy arrays, and performing basic operations. ## Additional Resources - [NumPy Documentation](https://numpy.org/) - [SciPy Documentation](https://scipy.github.io/devdocs/index.html) ## Discussion Before moving on to the next topic, **leave a comment below** with any questions or feedback about this topic. Additionally, you may ask for help if you're struggling with any concepts.

pip install numpy

import numpy as np

## Basic Operations with NumPy Arrays
- **Indexing**: Accessing individual elements or a subset of an array.
- **Array operations**: Perform operations like addition, subtraction, multiplication, and division on entire arrays.
- **Matrix multiplication**: Multiply two arrays together.

**Example of Basic Operations:**
```python
import numpy as np
arr = np.array([1, 2, 3, 4, 5])
print(arr * 2)  # Output: [2 4 6 8 10]

arr2 = np.array([[1, 2], [3, 4]])
arr3 = np.array([[5, 6], [7, 8]])

# Matrix multiplication
print(np.matmul(arr2, arr3))  # Output: [[19 22], [43 50]]

import numpy as np
arr = np.array([3, 1, 4, 2, 5])

# Compute min and max
print(np.min(arr))  # Output: 1
print(np.max(arr))  # Output: 5

# Compute mean and median
print(np.mean(arr))  # Output: 3.0
print(np.median(arr))  # Output: 3.0