Rendezvous: Difference between revisions

=={{header|Python}}==

{{works with|Python|3.7}}

<lang python>"""An approximation of the rendezvous pattern found in Ada using asyncio."""

from __future__ import annotations

import asyncio

import sys

from typing import Optional

from typing import TextIO

class OutOfInkError(Exception):

"""Exception raised when a printer is out of ink."""

class Printer:

def __init__(self, name: str, backup: Optional[Printer]):

self.name = name

self.backup = backup

self.ink_level: int = 5

self.output_stream: TextIO = sys.stdout

async def print(self, msg):

if self.ink_level <= 0:

if self.backup:

await self.backup.print(msg)

else:

raise OutOfInkError(self.name)

else:

self.ink_level -= 1

self.output_stream.write(f"({self.name}): {msg}\n")

async def main():

reserve = Printer("reserve", None)

main = Printer("main", reserve)

humpty_lines = [

"Humpty Dumpty sat on a wall.",

"Humpty Dumpty had a great fall.",

"All the king's horses and all the king's men,",

"Couldn't put Humpty together again.",

]

goose_lines = [

"Old Mother Goose,",

"When she wanted to wander,",

"Would ride through the air,",

"On a very fine gander.",

"Jack's mother came in,",

"And caught the goose soon,",

"And mounting its back,",

"Flew up to the moon.",

]

async def print_humpty():

for line in humpty_lines:

try:

task = asyncio.Task(main.print(line))

await task

except OutOfInkError:

print("\t Humpty Dumpty out of ink!")

break

async def print_goose():

for line in goose_lines:

try:

task = asyncio.Task(main.print(line))

await task

except OutOfInkError:

print("\t Mother Goose out of ink!")

break

await asyncio.gather(print_goose(), print_humpty())

if __name__ == "__main__":

asyncio.run(main(), debug=True)</lang>

{{out}}

<pre>

(main): Old Mother Goose,

(main): Humpty Dumpty sat on a wall.

(main): When she wanted to wander,

(main): Humpty Dumpty had a great fall.

(main): Would ride through the air,

(reserve): All the king's horses and all the king's men,

(reserve): On a very fine gander.

(reserve): Couldn't put Humpty together again.

(reserve): Jack's mother came in,

(reserve): And caught the goose soon,

Mother Goose out of ink!</pre>