Re: Pause a thread/ execfile()
On 26/10/09 12:28 PM, Babloo wrote: i have a small python application with GUI (frontend) which has various functions. I have a RUN button which runs python scripts in the background . It basically calls execfile() function internally which runs in a thread , to run the python script . I want to implement a PAUSE feature which would pause the running python script . So do that i have to either pause the thread in which execfile() runs or pause execfile itself . When the user presses RUN again then the python script should resume running . Any ideas how to pause the thread / pause execfile() . Any other ideas for the same would be helpful . Other ideas ? You could use job control signals if you are on unix. Try forking a child process instead of using a thread. Sending SIGSTOP to the forked child will stop/pause it, SIGCONT will resume it. -srp -- http://mail.python.org/mailman/listinfo/python-list
Re: How to declare python ints in C extensions?
Tony Houghton wrote:
I want to write python wrappers for the Linux DVB API. The underlying
structures and constants may change from time to time, and some of the
constants are generated from macros, so I think it would be better to
write the module in C rather than just copying the constants into pure
python code and using python's ioctl and struct modules.
The trouble is I can't find out how to define a simple python int
variable/constant in a C extension. The docs only seem to tell you how
to define functions/methods and new types.
For example, where the kernel header dvb/frontend.h defines:
typedef enum fe_type {
FE_QPSK,
FE_QAM,
FE_OFDM,
FE_ATSC
} fe_type_t;
I want to make them available as if there was a python module
dvb/frontend.py containing:
FE_QPSK = 0
FE_QAM = 1
FE_OFDM = 2
FE_ATSC = 3
but in real life the module would be dvb/frontendmodule.c.
Create Python Int objects for each of these constants and set them into
your module object's dictionary
foo = PyInt_FromLong(1L);
PyDict_SetItemString(PyModule_GetDict(your_module), foo, foo);
Py_DECREF(foo)
srp
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Re: select.select and socket.setblocking
Bryan Olson fakeaddr...@nowhere.org wrote: Where does this come up? Suppose that to take advantage of multi-core processors, our server runs as four processes, each with a single thread that responds to events via select(). Clients all connect to the same server port, so the socket listening on that port is shared by all four processes. A perfectly reasonable architecture (though with many more processes the simple implementation suffers the thundering herd problem). Which is why it is common for real world servers to serialize the select()/accept() code - usually via a file lock or a semaphore. -srp -- http://saju.net.in Two of our processors may be waiting on select() when a new connections comes in. The select() call returns in both processes, showing the socket ready for read, so both call accept() to complete the connection. The O.S. ensures that accept() [and recv()] are atomic, so one process gets the new connection; what happens in the other depends on whether we use a blocking or non-blocking socket, and clearly we want non-blocking. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: select.select and socket.setblocking
On Dec 31, 2:01 pm, Francesco Bochicchio bock...@virgilio.it wrote: Grant Edwards ha scritto: On 2008-12-30, Francesco Bochicchio bock...@virgilio.it wrote: 3. AFAIK (sorry, I feel acronym-ly today ;), there is no difference in select between blocking and non-blocking mode. The difference is in the recv (again, assuming that you use TCP as protocol, that is AF_INET, SOCK_STREAM), which in the blocking case would wait to receive all the bytes that you requested, No, in blocking mode it will wait to receive _some_ data (1 or more bytes). The requested amount is strictly an upper limit: recv won't return more than the requested number of bytes, but it might return less. Uhm. In my experience, with TCP protocol recv only returned less than the required bytes if the remote end disconnects. I always check the What if the sending end actually sent less than you asked for ? -srp returned value of recv and signal an error if the read bytes are less than the expected ones, but this error is never occurred (and its about 20 years that I use sockets in various languages and various flavor of unix and occasionally on windows. Maybe have always been lucky ? :-) And, on some unices system call recv also returns when a signal interrupts the syscall, but I half-remember reading that python recv in such a case repeat the system call by itself ... although this might be only my desire ... In non-blocking mode, it will always return immediately, either with some data, no data (other end closed), or an EAGAIN or EWOULDBLOCK error (I forget which). [...] I myself tend to avoid using non-blocking sockets, since blocking sockets are much easier to handle... That depends on whether you can tolerate blocking or not. In an event-loop, blocking is generally not allowed. What I usually do, when I cannot block is: - use socket in blocking mode - do a select with a very small timeout and do a recv only if the select returns with input events - (with TCP) do a recv for the exact amount of bytes that I expect ( this mean having a user protocol that carries the message size in the header, but this is usually the case ). This usually worked for me. If my process (or thread) has only to deal with socket I/O, I make a blocking select, and then make an 'exact' recv on whichever socket the select signals. Ciao FB -- http://mail.python.org/mailman/listinfo/python-list
Re: select.select and socket.setblocking
On Dec 31, 7:48 pm, Francesco Bochicchio bock...@virgilio.it wrote: ... Uhm. In my experience, with TCP protocol recv only returned less than the required bytes if the remote end disconnects. I always check the What if the sending end actually sent less than you asked for ? -srp In blocking mode and with TCP protocol, the recv waits until more bytes are received - mixing up the next message with the previous one and Is this correct ? IIRC even in blocking mode recv() can return with less bytes than requested, unless the MSG_WAITALL flag is supplied. Blocking mode only guarantees that recv() will wait for a message if none is available - but not that it *will* return the number of bytes requested. -srp then loosing the 'sync' and being unable to interpretate the received data - or the remote end disconnects. Yes this is bad, and is a good reason why socket receive should be handled in non-blocking mode if you receive data from untrusted sources. But luckily for me, as I said in the other post, I used socket mostly to communicate between specific applications on a private LAN or WAN, so I could afford to ignore the problem. Ciao FB -- http://mail.python.org/mailman/listinfo/python-list
Re: Can anyone suggest a good HTTP/1.1 web client?
On Dec 17, 1:18 am, Kottiyath n.kottiy...@gmail.com wrote: Hi all, I have to connect to a secure website every second to get the data and then post to it. I have been investigating on many web clients in python, but nothing fits the bill properly. The ones I tried implementing are: 1. httplib based - I created myself. (I cannot use urllib2 since I have to transfer files, and urllib2 doesnt have multipart content-type support) 2. Twisted web client. I also looked at mechanize etc too. The problems I face are - 1. I liked twisted a lot, but when I implemented it, I found that client support is there only for twisted.web and not twisted.web2. Since I connect to the same website every time, I would like to have persistent connections and since twisted.web is HTTP/1.0, persistent connection support is not yet there. Without persistent connections, I would have to have TCP connection handshake everytime and it is taking too much time. 2. Since I connect to the website every second, I have to have many connections running at the same time. I am worried that creating threads for each connection is going to be a big problem (esp if the server response is slow), since the processor will get swamped - especially since there are many other activities going on in the machine. 3. I would also like to pipe line the requests - esp if the response is slow. Other requirements: 1. HTTPS Support 2. Connection through proxy. You could take a look at pycurl - python bindings for libcurl. http://pycurl.sourceforge.net/ srp Is there any good web client which I can use straight up? Or would I have to implement the whole thing myself? It looks like a big beast and I was wondering whether python provides it straight up. Regards K -- http://mail.python.org/mailman/listinfo/python-list
Re: Python, threading
On Dec 11, 6:06 pm, SMALLp [EMAIL PROTECTED] wrote: Hy. I have a problem! I'm making multi thread application (client, server) using wxPython for GUI, and threading.Thread for threding. Clients connect and when they are connected (evry thread handles one connection) threads change main window. I neded tip how to make communication between threeds. Threads already share data your problem would likely be to synchronize the threads - threading.Sempahore threading.Lock will help Maybe you want some threads to wait while other thread(s) do some work ? - threading.Event threading.Condition The documentation on threading module is where you should start. -srp -- http://saju.net.in -- http://mail.python.org/mailman/listinfo/python-list
Re: How to convert uint64 in C into Python 32bit Object [ I am using Python2.2 ]
On Dec 11, 6:45 pm, Explore_Imagination [EMAIL PROTECTED]
wrote:
On Dec 11, 4:45 am, John Machin [EMAIL PROTECTED] wrote:
On Dec 11, 9:49 am, Explore_Imagination [EMAIL PROTECTED]
wrote:
Hi all
I am new to C and python ... I want to convert C data type uint64
variable into the Python 32bit Object. I am currently using Python 2.2
[ It is necessary to use it ]
Kindly give your suggestion how and in which way I can achieve this
task.
I'm not sure what you mean by the Python 32bit Object. A Python int
object holds a signed 32-bit integer. A Python long object holds a
signed integer of arbitrary size. You will need to convert your uint64
into a Python long; then, if necessary, check that the result will fit
in an int (result = sys.maxint).
If the C variable is in an 8-byte string that you have read from a
file, the unpack function in the struct module will do the job.
Assuming your computer is little-endian:
maxu64 = '\xff' * 8 # example input string
import struct
result = struct.unpack('Q', maxu64)[0]
result
18446744073709551615L 2 ** 64 - 1
18446744073709551615L
If however you mean that in C code you need to build a Python object
to pass over to Python code: According to the Python/C API Reference
Manual (http://www.python.org/doc/2.2.3/api/longObjects.html):
PyObject* PyLong_FromUnsignedLongLong(unsigned long long v)
Return value: New reference.
Returns a new PyLongObject object from a C unsigned long long, or
NULL on failure.
If however you mean something else,
HTH,
John
Thanks for your feedback ... Actually I want to pass unit64 variable
in C to python
but at the same time I want to have a generic code which should work
on both little-endian
and big endian architectures
Any suggestions ?
I am not sure if endianness comes into the picture. As long as sizeof
(uint64) == sizeof(unsigned long long) on your platform, python should
have no problem accepting the return value of
PyLong_FromUnsignedLongLong(uint64_var);
srp
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Re: Any way to loop through object variables?
On 28-May-08, at 9:49 PM, Gary Herron wrote: Dave Challis wrote: Hi, Just wondering if there's a way to iterate through all variables which an object has set? Specifically, I'm using the OptionParser module, which returns an options object, containing all command line options as object variables. I'd like to iterate over these rather than getting at them by name. Cheers, Dave For this object (and many others), you can get at the attributes with the vars(...) builtin. It returns a dictionary of attribute names and values. Also dir(object) will get you the list of attributes of that object. -srp Gary Herron -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
