Python 3.6+sysfunction

sys.set_asyncgen_hooks()

asynchronous code

Installs the asynchronous generator hooks: firstiter runs on the first iteration, finalizer when the generator is garbage-collected.

Syntax

sys.set_asyncgen_hooks(firstiter=..., finalizer=...)

This is an API for event loop authors: asyncio, trio and uvloop install the hooks themselves, and overriding them from application code breaks generator cleanup. Hooks are per thread; an omitted argument leaves that hook unchanged. Save the old hooks and restore them.

Examples

import sys
seen = []
old = sys.get_asyncgen_hooks()
sys.set_asyncgen_hooks(firstiter=lambda agen: seen.append(agen.__name__))
async def ticks():
    yield 1
g = ticks()
step = g.asend(None)
step.close()
sys.set_asyncgen_hooks(*old)
print(seen)  # → ['ticks']

See also

Open in the full glossarydocs.python.orgReport an inaccuracy