EX Installing Libraries

What are Libraries?

In programming, libraries are collections of pre-written code that provide reusable functions, classes, and methods to perform common tasks.
They help you avoid rewriting standard functionality and instead focus on the logic of your own project.
Python offers thousands of libraries for topics such as data processing, visualization, web development, and machine learning.

Why Do We Need Libraries?

Libraries are important because they:

  1. Save time – You can use ready-made solutions instead of coding everything from scratch.
  2. Increase reliability – Most libraries are well-tested and maintained by large communities.
  3. Ensure consistency – Using standard libraries keeps your code easy to understand and maintain.
  4. Expand functionality – Libraries give you access to advanced tools and algorithms.

Built-in Libraries in Python

When you install Python, it already comes with a large Standard Library.
These libraries are available immediately—no installation required.

Example:

import math

print(math.sqrt(25))  # Output: 5.0

Other built-in libraries include: os, datetime, random, json, and sys.

Installing External Libraries

If you need functionality that is not part of the standard library, you can install additional libraries from the Python Package Index (PyPI) using the tool pip.

You can run pip from:

  • the Terminal (on Windows, macOS, or Linux)

🧩 Option 1: Install via Terminal

  1. Open the Command Prompt (Windows) or Terminal (macOS/Linux).
  2. Type for example: 
    pip install pandas
  3. Wait until the installation completes successfully.

💡 On some systems, you may need to use pip3 instead of pip.

🔐 Note on Administrator Rights

If Python is installed system-wide (for example under C:\Program Files\Python39),
pip install may fail without admin rights.
In that case:

  1. Open the Command Prompt as Administrator, or
  2. Install the library for your user only: 
    pip install --user numpy

After Installing: Using a Library in Your Code

Once a library is installed, you can import it and use its functions:

import pandas as pd

data = pd.DataFrame({
    "Name": ["Alice", "Bob", "Charlie"],
    "Age": [25, 30, 35]
})

print(data)

✅ Summary

  • Python already includes many useful libraries.
  • You can install more using pip.
  • In Jupyter Notebook, use !pip install library_name.
  • Always restart the kernel after installing new packages.

Updated: