Except when they don't. Refer to MSDN. On Windows, it will return immediately with an error. This may be a Python oddity. Peculiar errnos from select 2 I've seen errnos 0 and 2 returned on Win32 for no reason I understood, apparently when passing empty read or write list. Detecting failed connects is done using exception list of select 2 On Unix, a failed connect will return an error upon reading or writing from the socket, and select will mark the socket as notified.
This example can serve only one incoming connection because it does not call accept in a cycle. Here instead of bind and listen it calls only connect and immediately sends data to the server. Then it receives bytes back, closes the socket, and prints the received data. All socket methods are blocking. For example, when it reads from a socket or writes to it the program can't do anything else.
One possible solution is to delegate working with clients to separate threads. However, creating threads and switching contexts between them is not really a cheap operation. To address this problem, there is a so-called asynchronous way of working with sockets.
The main idea is to delegate maintaining the socket's state to an operating system and letting it notify the program when there is something to read from the socket or when it is ready for writing.
As you can see, there is much more code than in the blocking Echo server. That is primarily because we have to maintain a set of queues for different lists of sockets, i. Creating server socket looks the same except for one line: server. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters. This allows another thread to cancel the wrapped stdin, and the fake readline can return — which is enough for cmd.
The next horrible hack I can think of is making a fake stdin that allows injection of characters — newline could be injected, getting the readline to return which can then be processed in cmd. The background runs a thread that does your long running code like maybe running a GUI mainloop , while the main thread runs the code that needs stdin in this case cmd. If the background thread needs to quit then it sends signals.
Leaving stdin alone really does seem to be the better solution in this case. You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email.
The Unix way: select The simpler solution is using select on sys. Note timeout is zero so select won't block at all. Treat available input immediately, but do something else if idle. A smaller number means more cpu usage, but a greater one means a more noticeable delay between input becoming available and the program starting to work on it. Standard Template Library. Python Python Tutorial.
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