What is the purpose of environment variables in the development and operation of applications?

Environment variables are dynamic values set in the operating system and accessible to an application during its runtime. They are used to store configuration data that can change depending on the environment (development, testing, production).

Main uses:

• Storing secrets (API keys, passwords) to avoid hardcoding them in the code.
• Configuring application parameters (server addresses, ports, modes of operation).
• Ensuring flexibility and convenience when deploying and transferring the application between environments.

Example in Python for reading an environment variable:

import os

api_key = os.getenv('API_KEY')  # Get the value of the API_KEY variable
if api_key:
    print('API key received')
else:
    print('API key not set')

Thus, environment variables help separate configuration from code and improve security and manageability of the application.