On Aug 20, 4:36 am, Phil Thompson <p...@riverbankcomputing.com> wrote: > On Fri, 19 Aug 2011 14:32:12 -0700 (PDT), Edgar Fuentes > > > > > > > > > > <fuente...@gmail.com> wrote: > > On Aug 19, 4:21 pm, Carl Banks <pavlovevide...@gmail.com> wrote: > >> On Friday, August 19, 2011 12:55:40 PM UTC-7, Edgar Fuentes wrote: > >> > On Aug 19, 1:56 pm, Phil Thompson > >> > wrote: > >> > > On Fri, 19 Aug 2011 10:15:20 -0700 (PDT), Edgar Fuentes > >> > > <fuen...@gmail.com> wrote: > >> > > > Dear friends, > > >> > > > I need execute an external program from a gui using PyQt4, to > avoid > >> > > > that hang the main thread, i must connect the signal > >> > > > "finished(int)" > >> > > > of a QProcess to work properly. > > >> > > > for example, why this program don't work? > > >> > > > from PyQt4.QtCore import QProcess > >> > > > pro = QProcess() # create QProcess object > >> > > > pro.connect(pro, SIGNAL('started()'), lambda > >> > > > x="started":print(x)) # connect > >> > > > pro.connect(pro, SIGNAL("finished(int)"), lambda > >> > > > x="finished":print(x)) > >> > > > pro.start('python',['hello.py']) # star hello.py > program > >> > > > (contain print("hello world!")) > >> > > > timeout = -1 > >> > > > pro.waitForFinished(timeout) > >> > > > print(pro.readAllStandardOutput().data()) > > >> > > > output: > > >> > > > started > >> > > > 0 > >> > > > b'hello world!\n' > > >> > > > see that not emit the signal finished(int) > > >> > > Yes it is, and your lambda slot is printing "0" which is the return > >> > > code > >> > > of the process. > > >> > > Phil > > >> > Ok, but the output should be: > > >> > started > >> > b'hello world!\n' > >> > finished > > >> > no?. > > >> > thanks Phil > > >> Two issues. First of all, your slot for the finished function does not > >> have the correct prototype, and it's accidentally not throwing an > >> exception because of your unnecessary use of default arguments. > Anyway, > >> to fix that, try this: > > >> pro.connect(pro, SIGNAL("finished(int)"), lambda v, > >> x="finished":print(x)) > > >> Notice that it adds an argument to the lambda (v) that accepts the int > >> argument of the signal. If you don't have that argument there, the int > >> argument goes into x, which is why Python prints 0 instead of > "finished". > > >> Second, processess run asynchrously, and because of line-buffering, IO > >> can output asynchronously, and so there's no guarantee what order > output > >> occurs. You might try calling the python subprocess with the '-u' > switch > >> to force unbuffered IO, which might be enough to force synchronous > output > >> (depending on how signal/slot and subprocess semantics are > implemented). > > >> Carl Banks > > > Thanks Carl, your intervention was very helpful for me, this solve my > > semantic error. I need to study more about signal/slots and process. > > In which case you should look at the modern, Pythonic connection syntax > rather than the old one... > > pro.started.connect(lambda: print("started")) > pro.finished.connect(lambda: print("finished")) > > Phil
Pythonic, great!, more straightforward. Thanks again Phil and Carl. best regards, Edgar Fuentes -- http://mail.python.org/mailman/listinfo/python-list