nest-asyncio2

1.7.2 · active · verified Sun Apr 12

nest-asyncio2 is a fork of the unmaintained `nest_asyncio` library, designed to patch `asyncio` to allow nested event loops. It addresses compatibility issues with Python 3.12+ and 3.14+ where the original library would fail. The current version is 1.7.2, and it receives updates as needed to maintain compatibility with newer Python versions and fix issues.

Warnings

breaking The original `nest_asyncio` library is unmaintained and incompatible with Python 3.12+ (e.g., `asyncio.current_task()` and `loop_factory` issues). `nest-asyncio2` is a fork specifically addressing these incompatibilities.
Fix: Migrate your `nest_asyncio` usage to `nest-asyncio2` by changing `import nest_asyncio` to `import nest_asyncio2` and updating `pip install` commands.
gotcha `nest-asyncio2.apply()` will warn if `asyncio` is already patched by `nest_asyncio` (on Python 3.12+) or can be configured to raise a `RuntimeError` by setting `error_on_mispatched=True`.
Fix: Ensure that only one of `nest_asyncio` or `nest-asyncio2` is applied. It's recommended to standardize on `nest-asyncio2` for modern Python versions.
gotcha On Python 3.12+, patched `asyncio.run()` might create a new event loop if none exists, which could lead to a `ResourceWarning: unclosed event loop` at exit. This warning is often hidden by default.
Fix: This is usually a cosmetic warning and doesn't require action. Be aware it might appear in specific environments or with custom warning filters.
gotcha In versions prior to `v1.7.2`, `asyncio.call_soon()` callbacks might not have been properly called during `asyncio.run()` in nested contexts.
Fix: Upgrade to `nest-asyncio2` v1.7.2 or later to ensure `call_soon()` callbacks are executed as expected.

Install

pip install nest-asyncio2 Install stable version

Imports

apply
```
import nest_asyncio2
nest_asyncio2.apply()
```
nest-asyncio2 is a direct replacement for the original `nest_asyncio` for Python 3.12+ compatibility. Ensure you use the correct package name.

Quickstart

This example demonstrates how to use `nest_asyncio2.apply()` to enable nested `asyncio.run()` calls. Without the patch, the inner `asyncio.run()` call would raise a `RuntimeError` because an event loop is already running.

import asyncio
import nest_asyncio2

async def inner_coroutine():
    print("Inner coroutine running.")
    await asyncio.sleep(0.01)
    print("Inner coroutine finished.")

async def outer_coroutine():
    print("Outer coroutine starting inner loop.")
    # This would normally fail with RuntimeError: This event loop is already running
    # but nest_asyncio2 allows it.
    await asyncio.run(inner_coroutine())
    print("Outer coroutine finished inner loop.")

# Apply the patch to allow nested event loops
nest_asyncio2.apply()

# Run the outer coroutine, which itself runs an inner event loop
print("Running outer event loop.")
asyncio.run(outer_coroutine())
print("Program finished.")

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