5 Best Ways to Get Application Version Using Python

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💡 Problem Formulation: When working with software applications, it’s often necessary to retrieve the version of an application to ensure compatibility or enforce version-specific functionality. In Python, there are multiple ways to find the version of an installed package or the Python interpreter itself. This article provides solutions on how to access version information, assuming we have an application named “example_app” and we want to retrieve its version as a string, e.g., “1.0.4”.

Method 1: Using the pkg_resources module

The pkg_resources module, which is part of the setuptools package, can be used to get the version of any installed package. It works by querying the metadata of installed distributions.

Here’s an example:

import pkg_resources

version = pkg_resources.get_distribution('example_app').version
print(version)

Output:

1.0.4

This code snippet uses pkg_resources.get_distribution() to fetch the distribution information of ‘example_app’ and then retrieves its version attribute. This is straightforward and works well with packages installed and managed by setuptools or pip.

Method 2: Using the importlib.metadata module

The importlib.metadata module provides functions for accessing an installed package’s metadata, introduced in Python 3.8. This is a more modern alternative to pkg_resources.

Here’s an example:

from importlib.metadata import version

version_info = version('example_app')
print(version_info)

Output:

1.0.4

The example uses importlib.metadata.version() to get the version of ‘example_app’. It’s a cleaner approach compared to pkg_resources and is included in the standard library for Python 3.8 and above.

Method 3: Accessing __version__ attribute

Many Python packages follow the convention of defining a __version__ attribute in their top-level module. This method assumes the package follows this convention.

Here’s an example:

import example_app

version = example_app.__version__
print(version)

Output:

1.0.4

The code simply imports ‘example_app’ and accesses its __version__ attribute. This is the most straightforward method but relies on the package developers including a __version__ attribute.

Method 4: Executing --version Argument with subprocess

For applications that support a --version command line argument, the subprocess module can be used to execute the application and capture its version output.

Here’s an example:

import subprocess

result = subprocess.run(['example_app', '--version'], stdout=subprocess.PIPE)
version = result.stdout.decode().strip()
print(version)

Output:

example_app 1.0.4

The subprocess.run() function executes ‘example_app’ with the argument ‘–version’, capturing its output. The version is then extracted by decoding and stripping the stdout. This requires the application to be executable from the command line with appropriate version argument support.

Bonus One-Liner Method 5: Using pip CLI with subprocess

You can also use the pip command line interface via the subprocess module to list installed packages and their versions, then parse the output for the desired application.

Here’s an example:

import subprocess

output = subprocess.check_output(['pip', 'list']).decode()
versions = dict([line.split()[:2] for line in output.split('\n')[2:] if line])
version = versions.get('example_app', 'Unknown')
print(version)

Output:

1.0.4

This one-liner first retrieves the output of pip list, decodes it, and then generates a dictionary mapping package names to their versions. The version of ‘example_app’ is then printed, defaulting to ‘Unknown’ if it’s not found. This method may be slower due to parsing a potentially large list of installed packages.

Summary/Discussion

  • Method 1: pkg_resources. Strength: Widely used with older versions of Python. Weakness: Not included in the standard library.
  • Method 2: importlib.metadata. Strength: Standard library support in Python 3.8+. Weakness: Not available for older Python versions.
  • Method 3: Accessing __version__. Strength: Simple and direct if implemented. Weakness: Depends on the package developer’s convention.
  • Method 4: Using subprocess to execute --version. Strength: Useful for CLI applications. Weakness: Requires the application to implement version output.
  • Method 5: Using pip CLI with subprocess. Strength: Utilizes pip, which is familiar to many Python developers. Weakness: Potentially slow and inefficient for large lists of installed packages.