add thread task and yield demos.

Author: junhuanchen

13.system/task.py

@@ -0,0 +1,44 @@
+
+import _thread
+
+import time
+
+class task(object):
+    
+    lock = _thread.allocate_lock()
+
+    def __init__(self):
+        self.alive = False
+
+    def run(self):
+        if task.lock.acquire():
+            while self.alive:
+                time.sleep(0.25)
+                print("running")
+            task.lock.release()
+        _thread.exit()
+        
+    def stop(self):
+        self.alive = False
+        if task.lock.acquire():
+            print("stop")
+            task.lock.release()
+
+    def start(self):
+        self.stop()
+        self.alive = True
+        if task.lock.acquire():
+            print("start")
+            _thread.start_new_thread(self.run, ())
+            task.lock.release()
+
+if __name__ == "__main__":
+    tmp = task()
+    tmp.start()
+    time.sleep(1)
+    tmp.start()
+    time.sleep(2)
+    tmp.start()
+    # time.sleep(3)
+    tmp.stop()
+

13.system/yield.py

@@ -0,0 +1,24 @@
+
+def event():
+	print('start yield')
+	one = yield 'get_one' # return next(task) and yield next(task.send('set_two'))
+	assert(one == 'set_two')
+	print(one)
+	yield 'get_two' # return next(task) and yield next(task.send('set_two'))
+	print('exit yield')
+	yield # yield next() to exit or raise StopIteration
+
+task = event()
+run_one = next(task) # need next(task) init and next(task) == task.send(None)
+# so next(task) => yield 'get_one' => run_one = 'get_one'
+assert(run_one == 'get_one')
+run_two = task.send('set_two')
+assert(run_two == 'get_two')
+print('run : ', run_one, ' and ', run_two)
+
+try:
+	next(task)
+	print('run end')
+	next(task) # will raise StopIteration
+except Exception as e:
+	print('yield StopIteration')