The way a timer works, especially the singleShot you are using, is that
once it is time to act it calls the function pointer you've provided.
You *must* provide a callable. Every tick of the timer is just calling
that callable with no parameters. You could provide a function pointer
to a function that will never return, but I think this will block your
GUI event loop (see below). I'd have to test it myself, but don't really
have the time right now, sorry.
If I understand you correctly, what you would like to happen is:
1. User clicks "Start"
2. newtime is called
3. newtime "creates" a new value
4. The time label (or other widget) gets updated with this new value
If you are just updating the time based on a certain interval, use a
QTimer without the singleShot, similar to what you are doing in your
example.
If updating a time is just an example in the code you've provided and
you would like to update a value I would suggest still using a QTimer or
using threads (QThread). It depends on why your "newtime" function needs
to be a long running loop that never returns.
If it is a long running loop that never returns because it continuously
updates the values, then you could change newtime to be "per iteration",
use QTimers, and call newtime every "tick" of the timer. So go from a
function like this:
def newtime(self):
i = 0
while True:
timeEdit.setText(str(i))
i += 1
to:
def newtime(self):
timeEdit.setText(str(self.i))
self.i += 1
If your loop is long running because it blocks on system IO (network
communications, file reading, database, etc.) then you should use
QThreads. Any type of long running code that runs in the main/GUI thread
will block your GUI and the user won't be able to interact. I suggest
researching PyQt Event loops, QThreads, and after that read
http://blog.qt.digia.com/blog/2010/06/17/youre-doing-it-wrong/
I've posted on this mailing list before helping users with their QThread
problems, if you look those up they may help.
Let me know what you decide to do and hopefully this rambling made sense.
-Dave
On 7/31/2013 7:10 PM, 吉文 wrote:
Hi, Dave, thank you very much for helping me. I am a newcomer to pyqt4,
so maybe my questions are low-level.Thanks again. If the function does
not have returns, can the button connect the function? The newtime
function realizes a loop to change the time every 1s, there is no
return. I want to click the 'start' button to begin the function, how to
realize that?
Thanks in advance
-Harry
2013/7/31 David Hoese <dho...@gmail.com <mailto:dho...@gmail.com>>
Hi Harry,
There are a couple missing things in your program. First, if you
read the exception you notice the line of the error and some
information about what's happening. The message you are getting is
saying that the argument to "connect" is not callable (meaning a
function or method or object with a __call__ method). If you look at
that line you'll see you are calling your "newTime" function and
passing what it returns. Instead what you want is to pass the
function itself. Right above that you use a lambda which will work,
but I would recommend using the functools.partial function:
http://docs.python.org/2/__library/functools.html#__functools.partial
<http://docs.python.org/2/library/functools.html#functools.partial>
You will want to remove the timer call that you have right before
declaring the button (line 19) otherwise the timer starts before the
"Start" button is clicked.
I think you could also use a QTimer without doing a singleShot, but
what you have works.
Please CC me in any replies. Good luck.
-Dave
On 7/31/13 6:00 AM, pyqt-request@__riverbankcomputing.com
<mailto:pyqt-requ...@riverbankcomputing.com> wrote:
Hi,all, I want to use a button to control when the program start
in pyqt4,
in other words, when I press the start button, the program will
work. I
wrote some code, but it doesn't work. please help me to correct
it. Thanks
in advance.
Best regards
Harry
import sys
from PyQt4 import QtGui
from PyQt4 import QtCore
import time
class Example(QtGui.QWidget):
def __init__(self):
super(Example, self).__init__()
self.initUI()
def initUI(self):
nowtime = '0000-00-00 00:00:00'
timeEdit = QtGui.QLabel(str(nowtime),__self)
timeEdit.resize(timeEdit.__sizeHint())
timeEdit.move(110,30)
QtCore.QTimer.singleShot(1000,__lambda:self.newtime(timeEdit))
startbtn = QtGui.QPushButton('Start', self)
startbtn.setToolTip('Click it to <b>start</b> the
program')
startbtn.clicked.connect(self.__newtime(timeEdit))
startbtn.resize(startbtn.__sizeHint())
startbtn.move(200, 340)
qbtn = QtGui.QPushButton('Quit', self)
qbtn.setToolTip('Click it and <b>quit</b> the program')
qbtn.clicked.connect(QtCore.__QCoreApplication.instance().__quit)
qbtn.resize(qbtn.sizeHint())
qbtn.move(400, 340)
self.setGeometry(300, 200, 600, 400)
self.setWindowTitle('Battery status')
self.show()
def newtime(self,timeEdit):
nowtime = time.strftime('%Y-%m-%d %H:%M:%S',
time.localtime())
timeEdit.setText(str(nowtime))
QtCore.QTimer.singleShot(1000,__lambda:self.newtime(timeEdit))
def main():
app = QtGui.QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
*when executing the program, there is something wrong:*
**
*Traceback (most recent call last):
File "C:\Python\calendar.py", line 62, in <module>
main()
File "C:\Python\calendar.py", line 57, in main
ex = Example()
File "C:\Python\calendar.py", line 15, in __init__
self.initUI()
File "C:\Python\calendar.py", line 32, in initUI
startbtn.clicked.connect(self.__newtime(timeEdit))
TypeError: connect() slot argument should be a callable or a
signal, not
'NoneType'*
_______________________________________________
PyQt mailing list PyQt@riverbankcomputing.com
http://www.riverbankcomputing.com/mailman/listinfo/pyqt
