Python：线程间同步输入和输出

Question

目前，我正在用Python做一个小项目，想实现一个两人聊天系统。

import socket
import threading

#Callback. Print doesn't work across threads
def data_recieved(data):
    print data

#Thread class to gather input
class socket_read(threading.Thread):
    sock = object
    def __init__(self, sock):
        threading.Thread.__init__(self)
        self.sock = sock
    def run(self):
        while True:
            data = self.sock.recv(1000)
            if (data == "\quitting\\"):
                return
            data_recieved(self.sock.recv(1000))

####################################################################################
server = False
uname = input("What's your username: ")
print "Now for the technical info..."
port = input("What port do I connect to ['any' if first]: ")
#This is the first client. Let it get an available port
if (port == "any"):
    server = True
    port = 9999
    err = True
    while err == True:
        try:
            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            sock.bind(('', port))
            err = False
        except:
            err = True
        sock.close()

    print "Bound to port #" + str(port)
    print "Waiting for client..."

    sock.listen(1)
    (channel, info) = sock.accept()
else:
    #This is the client. Just bind it tho a predisposed port
    host = input("What's the IP of the other client: ")
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((host, int(port)))

msg = ""
if (server == True):
    #Use the connection from accept
    reader = socket_read(channel)
else:
    #Use the actual socket
    reader = socket_read(sock)
reader.start()
while msg != 'quit':
    #Get the message...
    msg = uname + ": " + input("Message: ")
    try:
        #And send it
        if (server == True):
            #Use the connection from accept
            channel.send(msg)
        else:
            #Use direct socket
            sock.send(msg)
    except:
        break
reader.join()
channel.send("\quitting\\")
sock.close()

（我希望这些注释能帮到你）

不过，当我同时请求输入和接收另一个socket的消息时，我遇到了一个小的同步问题。我可以连接，但当我收到消息时，它并没有取消输入的提示。

换句话说，当我收到消息时，它会显示这个

Message: user: I got a message
#Flashing cursor here 

所以它并没有取消输入的提示。

而且，我只收到每隔一条消息。

有什么建议吗？

Answer 1

好的，抱歉这么快就回答了我自己的问题，但在使用线程时，回调函数真的是太神奇了（至少在Linux的模型上是这样）。

总之，我做了这个：

import socket
import threading

def msg_loop(socket):
    msg = ""
    if (server == True):
        reader = socket_read(channel)
    else:
        reader = socket_read(sock)
    reader.start()
    while msg != 'quit':
        msg = uname + " said : " + input("Message: ")
        print ""
        try:
            if (server == True):
                channel.send('null')
                channel.send(msg)
            else:
                sock.send('null')
                sock.send(msg)
        except:
            break

def data_recieved(data, socket):
    print "Hold on...\n\n" + data + "\n"
    msg_loop(socket)

class socket_read(threading.Thread):
    sock = object
    def __init__(self, sock):
        threading.Thread.__init__(self)
        self.sock = sock
    def run(self):
        while True:
            data = self.sock.recv(1000)
            if (data == "\quitting\\" or data == ''):
                return
            data_recieved(self.sock.recv(1000), self.sock)

####################################################################################
server = False
uname = str(input("What's your username: "))
print "Now for the technical stuff..."
port = input("What port do I connect to ['any' if first]: ")
if (port == "any"):
    server = True
    port = 9999
    err = True
    while err == True:
        try:
            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            sock.bind(('', port))
            err = False
        except:
            print "Socket #" + str(port) + " failed"
            err = True
            sock.close()
            port -= 1

    print "Bound to port #" + str(port)
    print "Waiting for client..."

    sock.listen(1)
    (channel, info) = sock.accept()
else:
    host = input("What's the IP of the other client: ")
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((host, int(port)))

if (server == True):
    msg_loop(channel)
else:
    msg_loop(sock)

reader.join()
channel.send("\quitting\\")
sock.close()

如你所见，我把消息循环作为回调函数加进去了。

另外要注意，我发送了一个空值，以避免“每隔一个”的问题。

还有，我在data_recieved的打印末尾加了一个换行符，以禁用换行。

（如果你喜欢这段代码，它在Windows上运行得不太好。这是因为，显然，Python在Windows上的线程模型执行得没有那么迅速。可以在你本地的Linux机器上试试。）

Answer 2

你遇到的问题其实不是同步方面的，而是界面展示的问题。我的建议是，选择一个用户界面工具包（比如 curses、wxPython 或 pyqt）来处理和用户的互动，这样会让你的生活轻松很多。使用 input() 函数虽然在写一些简单的代码时很方便，但它并不够高级。

如果你这样做了，就会发现其实根本不需要使用线程（这通常是个误区），你的问题就会像魔法一样消失！