Dependencies - Global Dependencies

🎯 What You'll Learn

• Learn how to add global dependencies to FastAPI applications
• Understand the difference between global and path operation dependencies
• Implement application-wide authentication and logging

📚 Theory

For some types of applications you might want to add dependencies to the whole application.

Similar to the way you can add dependencies to the path operation decorators, you can add them to the FastAPI application.

In that case, they will be applied to all the path operations in the application:

app = FastAPI(dependencies=[Depends(verify_token), Depends(verify_key)])

And all the ideas in the section about adding dependencies to the path operation decorators still apply, but in this case, to all of the path operations in the app.

Dependencies for Groups of Path Operations

Later, when reading about how to structure bigger applications (Bigger Applications - Multiple Files), possibly with multiple files, you will learn how to declare a single dependencies parameter for a group of path operations.

🔧 Key Concepts

• Global Dependencies: Dependencies applied to the entire FastAPI application
• Application-wide: Affects all path operations automatically
• No Duplication: Eliminates the need to add the same dependency to every endpoint

💡 Best Practices

• Use global dependencies for cross-cutting concerns like authentication
• Keep global dependencies lightweight to avoid performance overhead
• Consider using sub-dependencies for complex global logic
• Document global dependencies clearly for team members

🔗 Additional Resources

• FastAPI Dependencies Documentation
• Dependency Injection Patterns