Interview question

How do you write and run coroutines with async/await in Python? Python में async/await से coroutines कैसे लिखें और चलाएं?

Answer

import asyncio

# Defining a coroutine function
async def greet(name):
    print(f'Hello, {name}')
    await asyncio.sleep(1)  # simulates async work (I/O wait)
    print(f'Goodbye, {name}')
    return f'{name} greeted'

# Calling a coroutine function WITHOUT await just creates a coroutine object,
# it does NOT run the code yet
coro = greet('John')
print(coro)  # <coroutine object greet at 0x...>
# Need to actually run it via asyncio.run() or await inside another coroutine

# Running the top-level coroutine
asyncio.run(greet('John'))

# Running multiple coroutines CONCURRENTLY with gather
async def main():
    results = await asyncio.gather(
        greet('Alice'),
        greet('Bob')
    )
    print(results)  # ['Alice greeted', 'Bob greeted']

asyncio.run(main())

# Creating tasks explicitly for finer control (starts running immediately)
async def main2():
    task1 = asyncio.create_task(greet('Task1'))
    task2 = asyncio.create_task(greet('Task2'))
    # both tasks are now scheduled and running concurrently
    await task1
    await task2

asyncio.run(main2())

# Common mistake: forgetting await
async def broken():
    greet('Oops')  # missing 'await' - coroutine created but never runs!
    # RuntimeWarning: coroutine 'greet' was never awaited

import asyncio

async def greet(name):
    print(f'Hello, {name}')
    await asyncio.sleep(1)
    print(f'Goodbye, {name}')
    return f'{name} greeted'

# await के बिना call करने से सिर्फ coroutine object बनता है, चलता नहीं
coro = greet('John')
print(coro)  # coroutine object

# Top-level coroutine चलाना
asyncio.run(greet('John'))

# gather से concurrently चलाना
async def main():
    results = await asyncio.gather(
        greet('Alice'),
        greet('Bob')
    )
    print(results)

asyncio.run(main())

# create_task से tasks बनाना
async def main2():
    task1 = asyncio.create_task(greet('Task1'))
    task2 = asyncio.create_task(greet('Task2'))
    await task1
    await task2

asyncio.run(main2())

# Common गलती: await भूलना
async def broken():
    greet('Oops')  # 'await' missing - कभी नहीं चलेगा!
    # RuntimeWarning

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