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# test asyncio.gather() function
try:
import asyncio
except ImportError:
print("SKIP")
raise SystemExit
async def factorial(name, number):
f = 1
for i in range(2, number + 1):
print("Task {}: Compute factorial({})...".format(name, i))
await asyncio.sleep(0.01)
f *= i
print("Task {}: factorial({}) = {}".format(name, number, f))
return f
async def task(id, t=0.1):
print("start", id)
await asyncio.sleep(t)
print("end", id)
return id
async def task_loop(id):
print("task_loop start", id)
while True:
await asyncio.sleep(0.1)
print("task_loop loop", id)
async def task_raise(id, t=0.1):
print("task_raise start", id)
await asyncio.sleep(t)
print("task_raise raise", id)
raise ValueError(id)
async def gather_task(t0, t1):
print("gather_task")
await asyncio.gather(t0, t1)
print("gather_task2")
async def main():
# Simple gather with return values
print(await asyncio.gather(factorial("A", 2), factorial("B", 3), factorial("C", 4)))
print("====")
# Gather with no awaitables
print(await asyncio.gather())
print("====")
# Test return_exceptions, where one task is cancelled and the other finishes normally
tasks = [asyncio.create_task(task(1)), asyncio.create_task(task(2))]
tasks[0].cancel()
print(await asyncio.gather(*tasks, return_exceptions=True))
print("====")
# Test return_exceptions, where one task raises an exception and the other finishes normally.
tasks = [asyncio.create_task(task(1)), asyncio.create_task(task_raise(2))]
print(await asyncio.gather(*tasks, return_exceptions=True))
print("====")
# Test case where one task raises an exception and other task keeps running.
tasks = [asyncio.create_task(task_loop(1)), asyncio.create_task(task_raise(2))]
try:
await asyncio.gather(*tasks)
except ValueError as er:
print(repr(er))
print(tasks[0].done(), tasks[1].done())
for t in tasks:
t.cancel()
await asyncio.sleep(0.2)
print("====")
# Test case where both tasks raise an exception.
# Use t=0 so they raise one after the other, between the gather starting and finishing.
tasks = [asyncio.create_task(task_raise(1, t=0)), asyncio.create_task(task_raise(2, t=0))]
try:
await asyncio.gather(*tasks)
except ValueError as er:
print(repr(er))
print(tasks[0].done(), tasks[1].done())
print("====")
# Cancel a multi gather.
t = asyncio.create_task(gather_task(task(1), task(2)))
await asyncio.sleep(0.05)
t.cancel()
await asyncio.sleep(0.2)
# Test edge cases where the gather is cancelled just as tasks are created and ending.
for i in range(1, 4):
print("====")
t = asyncio.create_task(gather_task(task(1, t=0), task(2, t=0)))
for _ in range(i):
await asyncio.sleep(0)
t.cancel()
await asyncio.sleep(0.2)
asyncio.run(main())
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