Python asynchronous programming: Reveal the essence of asynchronous programming and optimize code performance

Asynchronous Programming , Asynchronous Programming in English, means that certain tasks in the program can be executed concurrently without waiting for other tasks to be completed, thus improving the overall operating efficiency of the program. In python, the asyncio module is the main tool for implementing asynchronous programming. It provides coroutines, event loops, and other components required for asynchronous programming.

Coroutine: Coroutine is a special function that can be suspended and then resume execution, just like threads, but coroutines are lighter than threads order of magnitude, memory consumption is lower. The coroutine is declared by the async keyword and execution is suspended at the await keyword.

Event loop: Event loop (Event Loop) is the core concept in asynchronous programming. It is a continuously running loop that is responsible for scheduling tasks between coroutines and handling I/O events. When a coroutine calls await, it is automatically suspended, and the event loop continues executing other coroutines. When an I/O event occurs, the event loop wakes up the corresponding coroutine to continue execution.

Asynchronous I/O: Due to the existence of GIL (Global Interpreter Lock), Multiple threads in Python cannot be truly parallel Run CPU-intensive tasks. Asynchronous I/O can solve this problem. It allows the program to continue performing other tasks while waiting for I/O operations to complete, thereby significantly improving the performance of the program.

Demo code:

import asyncio

async def get_html(url):
async with aioHttp.ClientSession() as session:
async with session.get(url) as response:
return await response.text()

async def main():
# 并发地获取多个网页的HTML内容
urls = ["https://www.example.com", "https://www.example2.com", "https://www.example3.com"]
tasks = [get_html(url) for url in urls]
html_content = await asyncio.gather(*tasks)

# 处理获取到的HTML内容
for content in html_content:
print(content)

if __name__ == "__main__":
asyncio.run(main())

In this example, we use the aiohttp library to perform asynchronous I/O operations and obtain the HTML content of multiple web pages in parallel. Due to asyncio's coroutines and event loops, the HTML content of multiple web pages can be obtained at the same time, thus significantly improving the performance of the program.

The advantages of asynchronous programming are very obvious. It can improve the concurrency and response speed of the program, reduce latency, and reduce resource consumption. In

high concurrency

and low-latency application scenarios, asynchronous programming is an indispensable technology.

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