Async Programming

Asyncio Fundamentals

Understanding Asynchronous Programming

• Synchronous vs asynchronous execution
• Blocking vs non-blocking operations
• Concurrency vs parallelism
• Event loop concept

Basic Asyncio

• async def for coroutine functions
• await keyword
• Running coroutines with asyncio.run()
• Event loop basics

Coroutines

• Creating coroutines
• Calling coroutines
• Coroutine objects
• Coroutine chaining

Async/Await Patterns

Basic Patterns

• Sequential execution with await
• Concurrent execution with asyncio.gather()
• Running tasks concurrently with asyncio.create_task()
• Waiting for multiple coroutines

Error Handling

• Exception handling in async functions
• asyncio.wait_for() for timeouts
• Cancelling tasks
• Handling task exceptions

Common Patterns

• Producer-consumer pattern
• Rate limiting
• Retry logic
• Background tasks

Concurrent Programming

Tasks and Futures

• Creating tasks
• Task groups
• Future objects
• Waiting for futures

Synchronization Primitives

• asyncio.Lock for mutual exclusion
• asyncio.Semaphore for limiting concurrency
• asyncio.Event for signaling
• asyncio.Condition for complex coordination

Queues

• asyncio.Queue for async queues
• Producer-consumer with queues
• Priority queues
• LifoQueue

Working with Synchronous Code

• Running blocking code in executor
• asyncio.to_thread() for CPU-bound tasks
• loop.run_in_executor() for I/O-bound tasks

Interview Questions

1. What is the difference between async and await?
2. How does asyncio differ from threading?
3. When should you use asyncio.gather() vs asyncio.create_task()?
4. How do you handle exceptions in async code?
5. What is an event loop and how does it work?

Coding Practice

1. Write an async function that fetches data from multiple URLs concurrently.
2. Implement an async rate limiter using Semaphore.
3. Create an async producer-consumer pattern with a queue.
4. Write an async function with timeout handling.
5. Implement an async retry mechanism for failed operations.

Resources

• Asyncio Documentation: https://docs.python.org/3/library/asyncio.html
• Real Python Async Guide: https://realpython.com/async-io-python/
• Async Patterns: https://docs.python.org/3/library/asyncio-task.html