What is the difference between asyncio and synchronous?

Mar 24, 2024 ยท 2 min read

Python includes both synchronous and asynchronous programming capabilities. But when should you use each one?

Synchronous Code

By default, Python code executes synchronously. This means statements are run one after another, blocking the next line from running until the current one finishes:


Here "Second" won't print until "First" is done. This makes code easy to reason about, but inefficient if parts could run in parallel.

Asynchronous Code with asyncio

The asyncio module lets you write asynchronous code which can execute multiple functions seemingly in parallel:

import asyncio

async def print_first():

async def print_second():   

Now both prints can run at the same time without blocking.

Behind the scenes, asyncio relies on cooperative multitasking - each coroutine yields control back to the event loop periodically so others can run.

When to Use Each

Use synchronous code for:

  • Simple scripts with a linear flow
  • CPU-bound processing
  • Use asyncio for:

  • I/O-bound work like network calls
  • Parallel execution when order doesn't matter
  • Concurrency within a single thread
  • The choice depends on your use case. Asyncio works great for I/O latency but doesn't help for intensive CPU tasks.

    Overall asyncio enables efficient concurrent code in Python. But synchronous execution still shines for straightforward sequences. Choose the right tool for the job!

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