[Solved] Why does this Flask async task code cause an error? from flask import Flask app = Flask(__name__) @app.route('/') def index():... Why does this Flask async task code cause an error? | Flask

Flask - Background Tasks

Why does this Flask async task code cause an error?

from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    import asyncio
    asyncio.run(background_task())
    return 'Done'

def background_task():
    print('Running')

AFlask does not support any async code.

Bbackground_task() must be decorated with @app.task.

CThe print statement is not allowed in async functions.

Dasyncio.run() cannot be called inside an already running event loop like Flask's.

Step-by-Step Solution

Solution:

Step 1: Understand asyncio.run() usage
asyncio.run() starts a new event loop and cannot be called inside an existing one.
Step 2: Recognize Flask's event loop context
Flask may already run inside an event loop, so calling asyncio.run() inside route causes error.
Final Answer:
asyncio.run() cannot be called inside an already running event loop like Flask's. -> Option D
Quick Check:
asyncio.run() inside event loop causes error [OK]

Quick Trick: Don't call asyncio.run() inside Flask route [OK]

Common Mistakes:

MISTAKES

Thinking Flask disallows all async code
Believing print is invalid in async
Confusing Flask tasks with Celery tasks

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More Flask Quizzes

Why does this Flask async task code cause an error?

Step 1: Understand asyncio.run() usage

Step 2: Recognize Flask's event loop context

Final Answer:

Quick Check:

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