all section 8 ex

cofollow.py

@@ -26,8 +26,17 @@ def consumer(func):
 @consumer
 def printer():
     while True:
-        item = yield
-        print(item)
+        try:
+            item = yield
+            print(item)
+        except Exception as e:
+            print(f'ERROR: {repr(e)}')
+
+
+def receive(expected_type):
+    msg = yield
+    assert isinstance(msg, expected_type), f'Expected type {expected_type}'
+    return msg
 
 
 if __name__ == '__main__':

coticker.py

@@ -1,6 +1,6 @@
 import csv
 
-from cofollow import consumer
+from cofollow import consumer, receive
 from tableformat import create_formatter
 from ticker import Ticker
 
@@ -13,21 +13,21 @@ def to_csv(target):
 
     reader = csv.reader(producer())
     while True:
-        line = yield
+        line = yield from receive(str)
         target.send(next(reader))
 
 
 @consumer
 def create_ticker(target):
     while True:
-        row = yield
+        row = yield from receive(list)
         target.send(Ticker.from_row(row))
 
 
 @consumer
 def negchange(target):
     while True:
-        record = yield
+        record = yield from receive(Ticker)
         if record.change < 0:
             target.send(record)
 
@@ -37,7 +37,7 @@ def ticker(fmt, fields):
     formatter = create_formatter(fmt)
     formatter.headings(fields)
     while True:
-        rec = yield
+        rec = yield from receive(Ticker)
         row = [getattr(rec, name) for name in fields]
         formatter.row(row)
 

follow.py

@@ -3,14 +3,17 @@ import time
 
 
 def follow(filename):
-    f = open(filename)
-    f.seek(0, os.SEEK_END)
-    while True:
-        line = f.readline()
-        if line == '':
-            time.sleep(0.1)
-            continue
-        yield line
+    try:
+        with open(filename, 'r') as f:
+            f.seek(0, os.SEEK_END)
+            while True:
+                line = f.readline()
+                if line == '':
+                    time.sleep(0.1)
+                    continue
+                yield line
+    except GeneratorExit:
+        print('Following Done')
 
 
 if __name__ == '__main__':

multitask.py

@@ -0,0 +1,33 @@
+from collections import deque
+
+tasks = deque()
+def run():
+    while tasks:
+        task = tasks.popleft()
+        try:
+            task.send(None)
+            tasks.append(task)
+        except StopIteration:
+            print('Task done')
+
+
+def countdown(n):
+    while n > 0:
+        print('T-minus', n)
+        yield
+        n -= 1
+
+
+def countup(n):
+    x = 0
+    while x < n:
+        print('Up we go', x)
+        yield
+        x += 1
+
+
+if __name__ == '__main__':
+    tasks.append(countdown(10))
+    tasks.append(countdown(5))
+    tasks.append(countup(20))
+    run()

server.py

@@ -0,0 +1,78 @@
+from collections import deque
+from select import select
+from socket import AF_INET, SO_REUSEADDR, SOCK_STREAM, SOL_SOCKET, socket
+from types import coroutine
+
+tasks = deque()
+recv_wait = {}
+send_wait = {}
+
+
+def run():
+    while any([tasks, recv_wait, send_wait]):
+        while not tasks:
+            can_recv, can_send, _ = select(recv_wait, send_wait, [])
+            for s in can_recv:
+                tasks.append(recv_wait.pop(s))
+            for s in can_send:
+                tasks.append(send_wait.pop(s))
+        task = tasks.popleft()
+        try:
+            reason, resource = task.send(None)
+            if reason == 'recv':
+                recv_wait[resource] = task
+            elif reason == 'send':
+                send_wait[resource] = task
+            else:
+                raise RuntimeError(f'Unknown reason {reason}')
+        except StopIteration:
+            print('Task done')
+
+
+class GenSocket:
+    def __init__(self, sock):
+        self.sock = sock
+
+    @coroutine
+    def accept(self):
+        yield 'recv', self.sock
+        client, addr = self.sock.accept()
+        return GenSocket(client), addr
+
+    @coroutine
+    def recv(self, maxsize):
+        yield 'recv', self.sock
+        return self.sock.recv(maxsize)
+
+    @coroutine
+    def send(self, data):
+        yield 'send', self.sock
+        return self.sock.send(data)
+
+    def __getattr__(self, name):
+        return getattr(self.sock, name)
+
+
+async def tcp_server(address, handler):
+    sock = GenSocket(socket(AF_INET, SOCK_STREAM))
+    sock.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
+    sock.bind(address)
+    sock.listen(5)
+    while True:
+        client, addr = await sock.accept()
+        tasks.append(handler(client, addr))
+
+
+async def echo_handler(client, address):
+    print('Connection from', address)
+    while True:
+        data = await client.recv(1000)
+        if not data:
+            break
+        await client.send(b'GOT: ' + data)
+    print('Connection closed')
+
+
+if __name__ == '__main__':
+    tasks.append(tcp_server(('', 25000), echo_handler))
+    run()