Python pip

Learning Objectives

In this lesson, you will learn how Python packages are installed and managed using pip.

What Is pip?

pip is Python's standard package installer. It allows you to install and manage packages from the Python Package Index and other package sources.

Python itself provides many built-in modules, but developers often need additional functionality. pip makes installing those external packages much easier.

python -m pip install requests

This command tells pip to install the requests package.

Why Use pip?

Modern Python applications often depend on many third-party packages.

For example, a data-analysis application might use packages such as NumPy, Pandas and Matplotlib.

A web application might use Flask or FastAPI.

Instead of manually downloading and configuring every library, pip provides a consistent way to install them.

Python Packages

A package is a collection of Python code that can be installed and reused in your projects.

Popular packages provide functionality for:

• Data analysis
• Machine learning
• Web development
• HTTP requests
• Data visualization
• Database access
• Automation

For example, after installing requests, you can write:

import requests

response = requests.get("https://example.com")

print(response.status_code)

The package provides functionality that is not part of Python's basic language syntax.

Checking Whether pip Is Installed

You can check pip from your terminal or command prompt.

python -m pip --version

On some systems, the Python command may be python3.

python3 -m pip --version

On Windows, the Python launcher can also be used:

py -m pip --version

Installing Packages

The basic installation command is:

python -m pip install package_name

For example:

python -m pip install requests

After installation, the package can be imported into your Python program.

import requests

print("Requests is ready!")

Installing a Specific Version

Sometimes your project requires a particular version of a package.

Use the == operator:

python -m pip install requests==2.32.3

You can also specify version ranges.

python -m pip install "requests>=2.30,<3.0"

Version constraints become particularly important in professional projects where dependency compatibility matters.

Upgrading Packages

To upgrade an installed package, use --upgrade.

python -m pip install --upgrade requests

Short form:

python -m pip install -U requests

Uninstalling Packages

If a package is no longer required, you can remove it using uninstall.

python -m pip uninstall requests

pip normally asks for confirmation before removing the package.

Proceed (Y/n)?

Listing Installed Packages

Use pip list to display packages installed in the current Python environment.

python -m pip list

You will typically see package names and their installed versions.

Package      Version
------------ -------
pip          25.x
requests     2.x
urllib3      2.x

The exact versions depend on your environment.

Inspecting a Package

Use pip show to inspect information about an installed package.

python -m pip show requests

Information may include:

• Package name
• Version
• Summary
• Installation location
• Dependencies

This can be useful when troubleshooting package installations.

Finding Packages

Python packages are commonly discovered through the Python Package Index, often called PyPI.

PyPI hosts a huge ecosystem of packages that Python developers can use in their projects.

Avoid blindly installing packages simply because their names look familiar.

requirements.txt

A Python project often needs multiple external packages.

Instead of manually recording every package, projects commonly use a file called requirements.txt.

requests==2.32.3
pandas==2.2.3
numpy==2.1.3
matplotlib==3.9.2

The file describes dependencies required by the project.

Installing Requirements

If a project contains a requirements.txt file, you can install all listed dependencies with:

python -m pip install -r requirements.txt

The -r option tells pip to read package requirements from the specified file.

project/
│
├── app.py
├── requirements.txt
└── README.md

pip freeze

The pip freeze command displays installed packages in a format suitable for a requirements file.

python -m pip freeze

You can save the result into a file:

python -m pip freeze > requirements.txt

The > operator redirects the command output into the file.

Why Use python -m pip?

You may see commands written in two different ways:

pip install requests

and:

python -m pip install requests

Both can invoke pip, but python -m pip explicitly connects pip with the Python interpreter represented by python.

Upgrading pip

pip itself is also a Python package and can be upgraded.

python -m pip install --upgrade pip

After upgrading, verify the installed version:

python -m pip --version

pip and Virtual Environments

One of the most important concepts in professional Python development is the use of virtual environments.

A virtual environment creates an isolated Python environment for a project.

This means different projects can use different package versions without interfering with each other.

python -m venv .venv

After activating the environment, pip installs packages into that environment.

We will study virtual environments in much more detail in the next dedicated lesson.

Common pip Mistakes

1. Using the Wrong Python Environment

You may install a package successfully but still receive an import error because your program is running with a different Python interpreter.

2. Installing Globally Without Thinking

Installing everything globally can create dependency conflicts between projects.

Virtual environments are generally a better approach for project dependencies.

3. Ignoring Version Compatibility

A package version may not support your Python version or may conflict with another dependency.

4. Running pip from the Wrong Directory

When installing from requirements.txt, make sure the file path is correct.

5. Trusting Every Package

External packages become part of your software supply chain. Check their reputation, documentation, maintenance and security before using them.

Practice Exercises

python -m pip --version

Mini Challenge — Prepare a Python Project

Imagine that you are preparing a small data-analysis project for another developer.

Suggested Dependencies

pandas
numpy
matplotlib

Suggested Commands

python -m venv .venv

python -m pip install pandas numpy matplotlib

python -m pip list

python -m pip freeze > requirements.txt

Knowledge Check

Lesson Summary

pip is one of the most important tools in the Python ecosystem because it allows developers to install and manage external packages.

You now have an important piece of professional Python workflow knowledge: installing and managing the libraries that your applications depend on.

In the next lesson, we will go deeper into Virtual Environments and learn how to create isolated Python environments for individual projects.