Can you explain the concept of dependency injection and how it is used in software development?

Dependency Injection (DI) is a design pattern where objects receive their dependencies from outside rather than creating them themselves. This increases modularity, testability, and flexibility of the code.

Example: instead of a class creating a database object itself, it receives it through a constructor or setter.

class Database:
    def query(self):
        return "data"

class Service:
    def __init__(self, db: Database):
        self.db = db

    def get_data(self):
        return self.db.query()

# Dependency injection
database = Database()
service = Service(database)
print(service.get_data())

This approach makes it easier to replace dependencies (for example, with mocks during testing) and improves code maintenance.