How to Check If Python Package Is Installed?

In Python, we often need to check if a package is installed before using it in our programs. Python provides several built-in methods to verify package installation in your environment.

A package is a directory containing one or more Python modules with an __init__.py file. Packages allow developers to create reusable code that can be imported into other programs, avoiding code duplication.

Using try-except

The most straightforward approach is to use a try-except block. When Python attempts to import an uninstalled package, it raises an ImportError exception.

Example

Here's how to check if a package exists using try-except ?

try:
    import Numpy as np
    print("The package is installed")
except ImportError as error:
    print(f"Import error: {error}")  

Import error: No module named 'Numpy'

Since Python is case-sensitive, "Numpy" (with capital N) doesn't exist. Let's try with the correct name ?

try:
    import numpy as np
    print("The package is installed")
except ImportError as error:
    print(f"Import error: {error}")  

The package is installed

Using importlib.util

The importlib.util module provides the find_spec() function to check package availability without actually importing it.

Example

This method checks if a package specification exists ?

import importlib.util

package = "django"
if importlib.util.find_spec(package) is None:
    print(f"{package} is not installed")
else:
    print(f"{package} is installed")

django is not installed

Using pkgutil Module

The pkgutil module provides utilities for working with packages. Its find_loader() function can locate package loaders.

Example

Here's how to use pkgutil to check package installation ?

import pkgutil

package = "pandas"
if pkgutil.find_loader(package) is None:
    print(f"{package} is not installed")
else:
    print(f"{package} is installed")

pandas is installed

Using pkg_resources Module

The pkg_resources module's get_distribution() function checks for installed packages and provides detailed package information.

Example

This method provides more detailed package information ?

import pkg_resources

package = "numpy"
try:
    distribution = pkg_resources.get_distribution(package)
    print(f"{package} is installed (version: {distribution.version})")
except pkg_resources.DistributionNotFound:
    print(f"{package} is not installed")

numpy is installed (version: 1.21.0)

Testing with a non-existent package ?

import pkg_resources

package = "nonexistent"
try:
    distribution = pkg_resources.get_distribution(package)
    print(f"{package} is installed (version: {distribution.version})")
except pkg_resources.DistributionNotFound:
    print(f"{package} is not installed")

nonexistent is not installed

Comparison

Conclusion

Use try-except for simple import-based checking, importlib.util.find_spec() for lightweight verification, or pkg_resources.get_distribution() when you need version information. Choose the method that best fits your specific requirements.