How to Check Python Package Version

Knowing the exact version of installed libraries is essential for reproducibility, debugging, and ensuring compatibility. Whether you are working in the terminal or writing a script, Python provides standard tools to retrieve this information.

This guide covers the best methods to check package versions: terminal commands, Python code, and outdated package detection.

Using the Terminal (CLI)

When investigating an environment or troubleshooting issues, pip commands provide quick access to version information.

Check a Specific Package

Use pip show to get detailed metadata about a single installed package:

pip show pandas

Output:

Name: pandas
Version: 2.1.4
Summary: Powerful data structures for data analysis...
Home-page: https://pandas.pydata.org
Author: The Pandas Development Team
License: BSD-3-Clause
Location: /usr/local/lib/python3.11/site-packages
Requires: numpy, python-dateutil, pytz
Required-by: seaborn, statsmodels

List All Packages

Use pip list to display a table of all installed packages with their versions:

pip list

Output:

Package         Version
--------------- -------
numpy           1.26.2
pandas          2.1.4
requests        2.31.0

Export for Deployment

Use pip freeze to generate output suitable for a requirements.txt file:

pip freeze > requirements.txt

Using Python Code

When your script needs to verify versions at runtime, for example, to check compatibility, use Python's import system.

The Modern Way: importlib.metadata (Recommended)

Since Python 3.8, the standard library provides importlib.metadata. This method retrieves version information without importing the package itself.

from importlib.metadata import version

pandas_ver = version("pandas")
print(f"Pandas version: {pandas_ver}")

packages = ["numpy", "requests", "pandas"]
for pkg in packages:
    try:
        print(f"{pkg}: {version(pkg)}")
    except Exception:
        print(f"{pkg}: not installed")

Version Comparison

For scripts that require minimum versions:

from importlib.metadata import version
from packaging.version import Version

pandas_ver = Version(version("pandas"))

if pandas_ver >= Version("2.0.0"):
    print("Using modern Pandas API")
else:
    print("Legacy Pandas version detected")

The Classic Way: __version__ Attribute

Most libraries expose a __version__ attribute, though this approach has drawbacks:

import pandas

print(pandas.__version__)

Finding Outdated Packages

Regularly checking for updates helps maintain security and access new features.

pip list --outdated

Output:

Package    Version   Latest    Type
---------- --------- --------- -----
numpy      1.24.0    1.26.2    wheel
requests   2.28.1    2.31.0    wheel
urllib3    1.26.12   2.1.0     wheel

Upgrade Outdated Packages

To upgrade a specific package:

pip install --upgrade numpy

To upgrade all outdated packages (use with caution):

pip list --outdated --format=freeze | cut -d= -f1 | xargs -n1 pip install --upgrade

Checking Versions in Virtual Environments

When working with multiple projects, ensure you are checking the correct environment:

which pip

python -m pip show pandas

Summary