In this article, we are going to see how to check whether the python package is installed or not.
By using Exception handling
In this method, we will use the try and except method. Under try, importing will be done. If the module is imported it will automatically moves forward else move to except and print the error messge.
Python3
try: import Module print("Already installed")except ImportError as e: print("Error -> ", e) |
Output:
Error -> No module named 'Module'
By using importlib package
In this, find_spec returns the None is module is not found
Syntax: find_spec(fullname, path, target=None)
Python3
import importlib.util# For illustrative purposes.package_name = 'Module'if importlib.util.find_spec(package_name) is None: print(package_name +" is not installed") |
Output:
Module is not installed
By using os module
Here we will execute pip list commands and store it into the list and then check the package is installed or not.
Python3
import osstream = os.popen('pip list')pip_list = stream.read()Package=list(pip_list.split(" "))# Count variablec = 0for i in Package: if "0.46\nopencv-python" in i: c = 1# Checking the value of c if c==1: print("Module Installed")else : print("Module is not installed") |
Output:
Module is not installed
By using the pkgutil module:
One alternative approach to check if a Python package is installed is to use the pkgutil module. The pkgutil module provides utilities for working with packages, and specifically includes a find_loader function that can be used to check if a package is installed.
Here is an example of how to use pkgutil.find_loader to check if a package is installed:
Python3
#import pkgutil# Check if the 'example' package is installedif pkgutil.find_loader('numpy') is not None: print("Package is installed")else: print("Package is not installed") |
Output:
Package is installed
Note that pkgutil.find_loader returns a ModuleLoader object if the package is installed, or None if it is not. Therefore, the condition in the if statement checks if the returned value is not None.
This approach has the advantage of being platform-agnostic and working for both Python 2 and Python 3. However, it does not provide information about where the package is installed or how it was installed (e.g. whether it was installed with pip or from a source distribution).
