Python includes a rich standard library, but many applications need additional packages for web development, data analysis, automation, testing, machine learning, database operations, and other specialized tasks.

These third-party packages can be installed using pip, the standard package installer for Python. The pip install command downloads the requested package, resolves its required dependencies, and installs everything into the selected Python environment.

Prerequisites

Before installing Python packages, make sure the following requirements are available:

Verify Python and pip

Before installing a package, verify that Python and pip are available on your computer.

Windows

py --version
py -m pip --version

Linux or macOS

python3 --version
python3 -m pip --version

If your computer uses python as the Python 3 command, you can use:

python --version
python -m pip --version

Example output:

Python 3.x.x
pip x.x.x from C:\Python\Lib\site-packages\pip

How Package Installation Works

Create a Virtual Environment

A virtual environment creates an isolated Python environment for a project. This helps prevent package and version conflicts between different projects.

Step 1: Create a Project Folder

mkdir package-demo
cd package-demo

Step 2: Create the Virtual Environment

python -m venv .venv

On Windows, you may also use:

py -m venv .venv

On Linux or macOS, you may need to use:

python3 -m venv .venv

Step 3: Activate on Windows Command Prompt

.venv\Scripts\activate

Step 3: Activate on Windows PowerShell

.venv\Scripts\Activate.ps1

Step 3: Activate on Linux or macOS

source .venv/bin/activate

After activation, the virtual environment name normally appears before the terminal prompt:

(.venv) C:\projects\package-demo>

Install a Python Package

The basic installation syntax is:

python -m pip install package_name

For example, install the Requests package:

python -m pip install requests

Example output:

Collecting requests
Downloading requests-2.x.x-py3-none-any.whl
Installing collected packages: requests
Successfully installed requests-2.x.x

The exact package version, filename, dependencies, and displayed output may differ in your environment.

Why Use python -m pip?

You may see packages installed with the shorter command:

pip install requests

However, the following form is generally clearer:

python -m pip install requests

The -m option asks the selected Python interpreter to run pip as a module. This helps ensure that the package is installed for the intended Python interpreter.

Verify the Installed Package

After installation, verify that the package is available.

Display Package Information

python -m pip show requests

Example output:

Name: requests
Version: 2.x.x
Summary: Python HTTP for Humans.
Location: C:\project\.venv\Lib\site-packages
Requires: certifi, charset-normalizer, idna, urllib3

List Installed Packages

python -m pip list

Import the Package

import requests

print("Requests version:", requests.__version__)

Possible output:

Requests version: 2.x.x

Use the Installed Package

Create a file named app.py and add the following code:

import requests

url = "https://example.com"

try:
    response = requests.get(url, timeout=10)

    print("Status code:", response.status_code)
    print("Content type:", response.headers.get("content-type"))

except requests.RequestException as error:
    print("Request failed:", error)

Run the program:

python app.py

Possible output:

Status code: 200
Content type: text/html

Install Multiple Packages

Multiple packages can be installed using one command:

python -m pip install requests flask pytest

pip processes the supplied package requirements and attempts to install compatible versions of the packages and their dependencies.

Install a Particular Package Version

Version specifiers can be used to control which package version should be installed.

Install an Exact Version

python -m pip install requests==2.32.3

Install a Minimum Version

python -m pip install "requests>=2.30.0"

Install Within a Version Range

python -m pip install "requests>=2.30.0,<3.0.0"

Upgrade an Installed Package

Use the --upgrade option to request a newer compatible package version:

python -m pip install --upgrade requests

The shorter form is:

python -m pip install -U requests

You can also upgrade or change the package to an exact version:

python -m pip install --upgrade requests==2.32.3

Reinstall a Package

If package files are damaged or need to be replaced, use:

python -m pip install --force-reinstall requests

Install Packages from requirements.txt

A requirements file allows a project to define multiple package requirements in one place.

Create a file named requirements.txt:

requests==2.32.3
Flask>=3.0,<4.0
pytest~=8.3

Install all packages listed in the file:

python -m pip install -r requirements.txt

Record Installed Packages

Use pip freeze to generate a list of installed packages:

python -m pip freeze > requirements.txt

Example generated file:

certifi==2025.4.26
charset-normalizer==3.4.2
idna==3.10
requests==2.32.3
urllib3==2.4.0

Review the generated file before sharing it because pip freeze records direct and supporting packages installed in the current environment.

Install from a Wheel File

A wheel is a built Python distribution whose filename ends with .whl. A local wheel file can be installed using:

python -m pip install ./dist/package_name-1.0.0-py3-none-any.whl

Install from a Source Archive

A source distribution archive can also be installed:

python -m pip install ./dist/package_name-1.0.0.tar.gz

Source installation may require compilers, system libraries, development headers, or other build tools.

Install a Local Python Project

A local Python project can be installed by supplying its directory path:

python -m pip install ./my_project

If the terminal is already inside the project directory, use:

python -m pip install .

A simplified project structure may look like this:

my_project/
|-- pyproject.toml
|-- README.md
|-- src/
|   `-- my_package/
|       `-- __init__.py
`-- tests/

Install a Project in Editable Mode

Editable installation is useful while actively developing a local Python package:

python -m pip install --editable .

The shorter form is:

python -m pip install -e .

Install Without Dependencies

Use --no-deps to prevent automatic dependency installation:

python -m pip install --no-deps requests

Install a Pre-release Package

Use the --pre option to allow compatible pre-release versions:

python -m pip install --pre package_name

Check Installed Dependencies

Use pip check to identify missing or incompatible dependencies:

python -m pip check

Successful output:

No broken requirements found.

Uninstall a Package

If a package is no longer required, uninstall it using:

python -m pip uninstall requests

pip normally requests confirmation before removing the package:

Proceed (Y/n)?

Common Installation Problems

Package Installation Security

Installing a package introduces third-party code into your Python environment. Package selection should therefore be treated as a software supply-chain decision.

Risky and Recommended Practices

Complete Installation Workflow

The following command sequence demonstrates a practical package installation workflow:

# Create the project directory
mkdir requests-demo
cd requests-demo

# Create a virtual environment
python -m venv .venv

# Activate the virtual environment
# Windows Command Prompt:
.venv\Scripts\activate

# Linux or macOS:
# source .venv/bin/activate

# Verify pip
python -m pip --version

# Install the package
python -m pip install requests

# Verify the installation
python -m pip show requests
python -m pip list
python -m pip check

# Record installed packages
python -m pip freeze > requirements.txt

# Deactivate when finished
deactivate

Hands-On Practice

Knowledge Check

python -m pip install package_name

python -m pip install package_name==1.0.0

python -m pip install -r requirements.txt

python -m pip install .

python -m pip install -e .

Package Installation Quick Reference

# Verify pip
python -m pip --version

# Install a package
python -m pip install requests

# Install multiple packages
python -m pip install requests flask pytest

# Install an exact version
python -m pip install requests==2.32.3

# Install within a version range
python -m pip install "requests>=2.30.0,<3.0.0"

# Upgrade a package
python -m pip install --upgrade requests

# Reinstall a package
python -m pip install --force-reinstall requests

# Install from requirements.txt
python -m pip install -r requirements.txt

# Install a local project
python -m pip install .

# Install in editable mode
python -m pip install -e .

# Install from a wheel
python -m pip install ./dist/package_name-1.0.0-py3-none-any.whl

# Install from a source archive
python -m pip install ./dist/package_name-1.0.0.tar.gz

# Display installed packages
python -m pip list

# Display package information
python -m pip show requests

# Check dependencies
python -m pip check

# Generate requirements.txt
python -m pip freeze > requirements.txt

# Uninstall a package
python -m pip uninstall requests

# Deactivate the virtual environment
deactivate

Summary