PythonHow-ToBeginner · 3 min read

How to Check Installed Packages in Python Quickly

To check installed packages in Python, use the pip list command in your terminal or command prompt. Alternatively, you can run pip freeze to see installed packages with their versions. You can also check packages programmatically using the pkg_resources module.

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Syntax

There are two main commands to check installed packages using pip:

pip list: Shows all installed packages with their versions.
pip freeze: Lists installed packages in a format suitable for requirements files.

To use these commands, open your terminal or command prompt and type them directly.

bash

pip list
pip freeze

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Example

This example shows how to list installed packages using pip list and how to check packages inside a Python script using pkg_resources.

python

import pkg_resources

# List installed packages programmatically
installed_packages = pkg_resources.working_set
packages_list = sorted([f"{i.key}=={i.version}" for i in installed_packages])
for package in packages_list:
    print(package)

Output

pip==23.0.1 setuptools==67.6.1 wheel==0.38.4

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Common Pitfalls

Some common mistakes when checking installed packages include:

Running pip commands in the wrong environment (e.g., system Python vs virtual environment).
Using pip without specifying the Python version, which can cause confusion if multiple Python versions are installed.
Expecting pip list to show packages installed by other means (like system package managers).

To avoid these, always activate your virtual environment first and use python -m pip list to ensure you check the correct Python installation.

bash

wrong:
pip list

right:
python -m pip list

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Quick Reference

Summary of commands to check installed Python packages:

Command	Description
pip list	Lists installed packages with versions
pip freeze	Lists installed packages in requirements format
python -m pip list	Runs pip list for the current Python interpreter
Use pkg_resources in Python	Check installed packages programmatically

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Key Takeaways

Use pip list or pip freeze in the terminal to see installed packages.

Run python -m pip list to ensure you check the correct Python environment.

Activate your virtual environment before checking packages to avoid confusion.

Use pkg_resources in Python code to list installed packages programmatically.

Remember that system package managers may install packages not shown by pip.