How to Install Modules in Python

What you’ll build or solve

You’ll install a Python module with pip, confirm you installed it for the same Python you run, and fix the most common “installed but can’t import” issues.

When this approach works best

This approach works best when you need to:

• Add a third-party package to a script, like requests for HTTP or rich for nicer terminal output.
• Install a library for a quick experiment or learning project.
• Recreate someone else’s setup using a requirements.txt file.

Avoid this approach when:

• The module is part of the standard library, like json, math, or pathlib. You don’t install those.
• You need project isolation or multiple projects with different versions. Use a virtual environment instead.

Prerequisites

• Python 3 installed
• A terminal you can run commands in
• Basic comfort running Python, for example:

python -c "print('hi')"

Step-by-step instructions

1) Install a module with python -m pip

Use python -m pip so pip matches the Python you are running.

python -m pip install requests

If your system uses python3:

python3 -m pip install requests

What to look for:

If you have both python and python3, use the one you normally run your scripts with.

2) Verify the module works

Check that pip sees the package:

python -m pip show requests

Then import it directly:

python -c "import requests; print(requests.__version__)"

If this runs without errors and prints a version, the install worked.

3) Install modules from requirements.txt

Use this when a project already lists its dependencies.

python -m pip install -r requirements.txt

If you need to create the file from your current environment:

python -m pip freeze > requirements.txt

This writes all installed packages and versions to the file.

4) Upgrade or uninstall a module

Upgrade a package:

python -m pip install --upgrade requests

Uninstall a package:

python -m pip uninstall requests

Examples you can copy

1) Install a package and run a quick import check

python -m pip install rich
python -c "from rich import print; print('[green]Installed![/green]')"

2) Install exactly what a project needs

python -m pip install -r requirements.txt
python -c "import requests; import flask; print('imports ok')"

3) Upgrade a package to get a bug fix

python -m pip install --upgrade requests
python -c "import requests; print(requests.__version__)"

Common mistakes and how to fix them

Mistake 1: Using pip that points to a different Python

You might run:

pip install requests
python -c "import requests"

Why it breaks:

pip can be connected to a different Python than python, so the install goes to the wrong place.

Correct approach:

python -m pip install requests
python -c "import requests; print(requests.__version__)"

Mistake 2: Installing the wrong thing because the name is different

You might run:

python -m pip install pil

Why it breaks:

Some libraries install under a different package name than you expect.

Correct approach:

python -m pip install pillow
python -c "from PIL import Image; print('PIL import ok')"

Mistake 3: Trying to install a standard library module

You might run:

python -m pip install json

Why it breaks:

Standard library modules ship with Python. Installing a third-party package with the same name can cause confusion.

Correct approach:

import json

data = json.loads('{"ok": true}')
print(data["ok"])

Troubleshooting

If you see ModuleNotFoundError right after installing, run these two commands and confirm they refer to the same Python:

python -c "import sys; print(sys.executable)"
python -m pip -V

If you see No module named pip, reinstall or enable pip:

python -m ensurepip --upgrade
python -m pip install --upgrade pip

If you hit a permissions error when installing, avoid system installs and use a virtual environment instead.

If you are behind a corporate network and installs fail, try upgrading pip first:

python -m pip install --upgrade pip

Quick recap

• Install with python -m pip install package to match pip to your Python.
• Verify with python -c "import package" and print a version if available.
• Install a full dependency list with python -m pip install -r requirements.txt.
• Upgrade with -upgrade, remove packages with pip uninstall.
• Use a virtual environment for project isolation when needed.