/Demo/threads/Generator.py

 1# Generator implementation using threads
 2
 3import sys
 4import thread
 5
 6class Killed(Exception):
 7    pass
 8
 9class Generator:
10    # Constructor
11    def __init__(self, func, args):
12        self.getlock = thread.allocate_lock()
13        self.putlock = thread.allocate_lock()
14        self.getlock.acquire()
15        self.putlock.acquire()
16        self.func = func
17        self.args = args
18        self.done = 0
19        self.killed = 0
20        thread.start_new_thread(self._start, ())
21
22    # Internal routine
23    def _start(self):
24        try:
25            self.putlock.acquire()
26            if not self.killed:
27                try:
28                    apply(self.func, (self,) + self.args)
29                except Killed:
30                    pass
31        finally:
32            if not self.killed:
33                self.done = 1
34                self.getlock.release()
35
36    # Called by producer for each value; raise Killed if no more needed
37    def put(self, value):
38        if self.killed:
39            raise TypeError, 'put() called on killed generator'
40        self.value = value
41        self.getlock.release()  # Resume consumer thread
42        self.putlock.acquire()  # Wait for next get() call
43        if self.killed:
44            raise Killed
45
46    # Called by producer to get next value; raise EOFError if no more
47    def get(self):
48        if self.killed:
49            raise TypeError, 'get() called on killed generator'
50        self.putlock.release()  # Resume producer thread
51        self.getlock.acquire()  # Wait for value to appear
52        if self.done:
53            raise EOFError  # Say there are no more values
54        return self.value
55
56    # Called by consumer if no more values wanted
57    def kill(self):
58        if self.killed:
59            raise TypeError, 'kill() called on killed generator'
60        self.killed = 1
61        self.putlock.release()
62
63    # Clone constructor
64    def clone(self):
65        return Generator(self.func, self.args)
66
67def pi(g):
68    k, a, b, a1, b1 = 2L, 4L, 1L, 12L, 4L
69    while 1:
70        # Next approximation
71        p, q, k = k*k, 2L*k+1L, k+1L
72        a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
73        # Print common digits
74        d, d1 = a//b, a1//b1
75        while d == d1:
76            g.put(int(d))
77            a, a1 = 10L*(a%b), 10L*(a1%b1)
78            d, d1 = a//b, a1//b1
79
80def test():
81    g = Generator(pi, ())
82    g.kill()
83    g = Generator(pi, ())
84    for i in range(10): print g.get(),
85    print
86    h = g.clone()
87    g.kill()
88    while 1:
89        print h.get(),
90        sys.stdout.flush()
91
92test()