Development/Tutorials/Python introduction to signals and slots - Revision history

Neverendingo: Text replace - "" to ""

2011-06-29T20:54:57Z

Text replace - "</code>" to "</syntaxhighlight>"

Neverendingo: Text replace - "`" to ""`


2011-06-29T20:45:37Z
Text replace - "<code>" to "<syntaxhighlight lang="text">"

				
				
				
				
			
			← Older revision
			Revision as of 20:45, 29 June 2011
			
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  </code>   </code>
    
− <code> + <syntaxhighlight lang="text">
  Output:   Output:
  0s starting in __main__   0s starting in __main__



Neverendingo: Text replace - "" to ""

2011-06-29T20:34:40Z
Text replace - "<code python>" to "<syntaxhighlight lang="python">"

				
				
				
				
			
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			Revision as of 20:34, 29 June 2011
			
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  We use the QObject.connect() method to connect signals and slots.     We use the QObject.connect() method to connect signals and slots.  
    
− <code python> + <syntaxhighlight lang="python">
  bool connect (QObject, SIGNAL(), callable, Qt.ConnectionType = Qt.AutoConnection)   bool connect (QObject, SIGNAL(), callable, Qt.ConnectionType = Qt.AutoConnection)
  </code>   </code>
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  '''Example'''   '''Example'''
− <code python> + <syntaxhighlight lang="python">
  from PyQt4.QtGui import *   from PyQt4.QtGui import *
  from PyQt4.QtCore import *   from PyQt4.QtCore import *
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  Only QObjects and objects inheriting from QObject can emit signals. To emit a signal we use the QObject.emit() method.   Only QObjects and objects inheriting from QObject can emit signals. To emit a signal we use the QObject.emit() method.
    
− <code python> + <syntaxhighlight lang="python">
  QObject.emit (self, SIGNAL(), ...)   QObject.emit (self, SIGNAL(), ...)
  </code>   </code>
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  '''Example:'''In this example we have a class with a function "afunc" that emits the signal "doSomePrinting()". The class also have function "bfunc" that prints "Hello world". First we create a object of the class then we connect the "doSomePrinting()" to "bfunc". After that we call "afunc". This will result in the printing of "Hello World" to the standard output   '''Example:'''In this example we have a class with a function "afunc" that emits the signal "doSomePrinting()". The class also have function "bfunc" that prints "Hello world". First we create a object of the class then we connect the "doSomePrinting()" to "bfunc". After that we call "afunc". This will result in the printing of "Hello World" to the standard output
    
− <code python> + <syntaxhighlight lang="python">
  import sys   import sys
  from time import time   from time import time
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  '''Example:'''   '''Example:'''
  This  example will create a slider and display it. Every time the value of the slider is changed the new value will be printed to the standard output. The references documentation for QSlider can be found [http://www.riverbankcomputing.com/Docs/PyQt4/html/qslider.html here], the valueChanged signal is inherited from [http://www.riverbankcomputing.com/Docs/PyQt4/html/qabstractslider.html QAbstractSlider]   This  example will create a slider and display it. Every time the value of the slider is changed the new value will be printed to the standard output. The references documentation for QSlider can be found [http://www.riverbankcomputing.com/Docs/PyQt4/html/qslider.html here], the valueChanged signal is inherited from [http://www.riverbankcomputing.com/Docs/PyQt4/html/qabstractslider.html QAbstractSlider]
− <code python> + <syntaxhighlight lang="python">
  from PyQt4.QtGui import *   from PyQt4.QtGui import *
  from PyQt4.QtCore import *   from PyQt4.QtCore import *
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  '''Example'''   '''Example'''
− <code python> + <syntaxhighlight lang="python">
  import sys   import sys
  from time import time   from time import time
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  '''The same example as above, using short-circuited signals. '''   '''The same example as above, using short-circuited signals. '''
− <code python> + <syntaxhighlight lang="python">
  import sys   import sys
  from time import time   from time import time
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  ==Signals and slots and threading==   ==Signals and slots and threading==
  To send signal across threads we have to use the Qt.QueuedConnection parameter. Without this parameter the code will be executed in the same thread.     To send signal across threads we have to use the Qt.QueuedConnection parameter. Without this parameter the code will be executed in the same thread.  
− <code python> + <syntaxhighlight lang="python">
  import sys   import sys
  from time import time   from time import time



Tampakrap: No 'work in progress' warning needed, this is a wiki, last edit 2007
2008-07-30T05:57:56Z
No 'work in progress' warning needed, this is a wiki, last edit 2007

				
				
				
				
			
			← Older revision
			Revision as of 05:57, 30 July 2008
			
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− {{warning|This tutorial is work in progress.}}  
−  
−  
  ==Abstract==   ==Abstract==
    



Tampakrap: /* Short-circuit Signal */
2007-10-08T22:31:34Z
‎Short-circuit Signal

				
				
				
				
			
			← Older revision
			Revision as of 22:31, 8 October 2007
			
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  ==Short-circuit Signal==   ==Short-circuit Signal==
− PyQt4 have a special type of signal called a short-circuit Signal. This signal implicitly declare all arguments to be of type PyQt_PyObject. Short-circuited signals does not have argument lists or parentheses. Short-circuited signals can only connected to python slots. + PyQt4 has a special type of signal called a short-circuit Signal. This signal implicitly declares all arguments to be of type PyQt_PyObject. Short-circuited signals do not have argument lists or parentheses. Short-circuited signals can only be connected to python slots.
    
  '''The same example as above, using short-circuited signals. '''   '''The same example as above, using short-circuited signals. '''
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           self.emit(SIGNAL("asignal"),msg)                 self.emit(SIGNAL("asignal"),msg)     
                         
−      def recive(self,msg): +      def receive(self,msg):
           print msg            print msg
    
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       app=QCoreApplication(sys.argv)        app=QCoreApplication(sys.argv)
       a=A()        a=A()
−      QObject.connect(a,SIGNAL("asignal"),a.recive) +      QObject.connect(a,SIGNAL("asignal"),a.receive)
       a.send()             a.send()     
                 



Tampakrap: /* Python objects as parameters */
2007-10-08T22:30:08Z
‎Python objects as parameters

				
				
				
				
			
			← Older revision
			Revision as of 22:30, 8 October 2007
			
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  ==Python objects as parameters==   ==Python objects as parameters==
− It's possible to send a python object of any type using PyQt_PyObject in the signature. This is recommended when both signal and slot is implemented in python. By using PyQt_PyObject we avoid unnecessary conversions between python objects and C++ types and it more consistent with python dynamically typed nature. + It's possible to send a python object of any type using PyQt_PyObject in the signature. This is recommended when both signal and slot is implemented in python. By using PyQt_PyObject we avoid unnecessary conversions between python objects and C++ types and it is more consistent with python dynamically typed nature.
    
  '''Example'''   '''Example'''



Tampakrap: /* Python objects as parameters */
2007-10-08T22:29:28Z
‎Python objects as parameters

				
				
				
				
			
			← Older revision
			Revision as of 22:29, 8 October 2007
			
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           self.emit(SIGNAL("asignal(PyQt_PyObject)"),msg)                 self.emit(SIGNAL("asignal(PyQt_PyObject)"),msg)     
                         
−      def recive(self,msg): +      def receive(self,msg):
           print msg            print msg
    
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       app=QCoreApplication(sys.argv)        app=QCoreApplication(sys.argv)
       a=A()        a=A()
−      QObject.connect(a,SIGNAL("asignal(PyQt_PyObject)"),a.recive) +      QObject.connect(a,SIGNAL("asignal(PyQt_PyObject)"),a.receive)
       a.send()             a.send()     
                 
       sys.exit(app.exec_())        sys.exit(app.exec_())
  </code>   </code>
−  
    
  ==Short-circuit Signal==   ==Short-circuit Signal==



Bygdog: /* Abstract */ accuracy, addition and conciseness
2007-03-18T16:50:12Z
‎Abstract:  accuracy, addition and conciseness

				
				
				
				
			
			← Older revision
			Revision as of 16:50, 18 March 2007
			
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  ==Abstract==   ==Abstract==
− The signal and slot architecture is design to simplify communication between objects.  It's a fact that GUI programming is mostly event driven.  The traditionally approach  to event driven programming is to use callbaks. Callbacks have a number of limitations that Qt tries to solve with it's signal and slot architecture. The concept is that every object can emit signals. For example when a button is clicked it emits a “clicked()” signal. Signals does not do anything alone, but when connected to a slot the code in the slot will be executed every time the signal is emitted. In python every function is a slot.  It's possible to connect one signal to multiple slots  
    
  + The signal and slot architecture is designed to simplify communication between objects.  GUI programming is mostly event-driven and conventionally uses callbacks.  The limitations of callbacks are partly resolved by the signal and slot architecture that Qt uses. The idea is that all objects can emit signals.
  + 
  + When a button is clicked, for example, it emits a “clicked()” signal. Signals do nothing alone, but once connected to a slot, the code in the slot will be executed whenever the signal is emitted.
  + 
  + In the Python programs, every function is a slot.  It is possible to connect one signal to multiple slots, and to connect slots consecutively. For instance, one event activates its slot and related subsequent events trigger another signal and the code in its slot to be executed.
    
  ==Prerequisites==   ==Prerequisites==



Axiom: /* Emitting signals */  It won't work unless you import sys first
2007-01-21T18:47:12Z
‎Emitting signals:   It won't work unless you import sys first

				
				
				
				
			
			← Older revision
			Revision as of 18:47, 21 January 2007
			
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  <code python>   <code python>
  + import sys
  from time import time   from time import time
  from PyQt4.QtCore import *   from PyQt4.QtCore import *



Tampakrap: fix typo
2007-01-15T23:26:08Z
fix typo

				
				
				
				
			
			← Older revision
			Revision as of 23:26, 15 January 2007
			
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  '''Example:'''   '''Example:'''
− This  example will create a slider and display it. Every time the value of the slider is changed the new value will be printed to the standard output. The references documentation for QSlider can be found [http://www.riverbankcomputing.com/Docs/PyQt4/html/qslider.html her], the valueChanged signal is inherited from [http://www.riverbankcomputing.com/Docs/PyQt4/html/qabstractslider.html QAbstractSlider] + This  example will create a slider and display it. Every time the value of the slider is changed the new value will be printed to the standard output. The references documentation for QSlider can be found [http://www.riverbankcomputing.com/Docs/PyQt4/html/qslider.html here], the valueChanged signal is inherited from [http://www.riverbankcomputing.com/Docs/PyQt4/html/qabstractslider.html QAbstractSlider]
  <code python>   <code python>
  from PyQt4.QtGui import *   from PyQt4.QtGui import *

@@ Line 16: / Line 16: @@
 <syntaxhighlight lang="python">
 bool connect (QObject, SIGNAL(), callable, Qt.ConnectionType = Qt.AutoConnection)
-</code>
+</syntaxhighlight>
 The first argument is the name of the object that is emitting the signal. The second argument is the signal, and the third argument is the slot. The slot has to bee a python callable object. Note that only QObjects and objects inheriting from QObject can emit signals.
@@ Line 39: / Line 39: @@
 #Start the evnt loop
 sys.exit(app.exec_())
-</code>
+</syntaxhighlight>
 ==Emitting signals==
@@ Line 46: / Line 46: @@
 <syntaxhighlight lang="python">
 QObject.emit (self, SIGNAL(), ...)
-</code>
+</syntaxhighlight>
 emit() is an object method, the self parameter is therefor automatically inserted by the python interpreter. The next argument is the signal we would like to emit, for example it could have been SIGNAL("myfirstsignal()") if we wanted to emit a signal with that name. The next parameters is optional parameters that can be sent with the signal, will come back to that in more detail later.
@@ Line 74: / Line 74: @@
      sys.exit(app.exec_())
-</code>
+</syntaxhighlight>
 ==Signals and slots with parameters==
@@ Line 101: / Line 101: @@
      #Start the evnt loop
      sys.exit(app.exec_())
-</code>
+</syntaxhighlight>
 ==Python objects as parameters==
@@ Line 133: / Line 133: @@
      sys.exit(app.exec_())
-</code>
+</syntaxhighlight>
 ==Short-circuit Signal==
@@ Line 165: / Line 165: @@
      sys.exit(app.exec_())
-</code>
+</syntaxhighlight>
 ==Signals and slots and threading==
@@ Line 205: / Line 205: @@
      sys.exit(app.exec_())
-</code>
+</syntaxhighlight>
 <syntaxhighlight lang="text">
@@ Line 224: / Line 224: @@
 s finished in a()
 s finished in __main__
-</code>
+</syntaxhighlight>
 ==QueuedConnections==
 [[Category:Python]]

← Older revision		Revision as of 05:57, 30 July 2008
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−	~~{{warning\|This tutorial is work in progress.}}~~
−
−
	==Abstract==		==Abstract==

← Older revision		Revision as of 16:50, 18 March 2007
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	==Abstract==		==Abstract==
−	The signal and slot architecture is design to simplify communication between objects. It's a fact that GUI programming is mostly event driven. The traditionally approach to event driven programming is to use callbaks. Callbacks have a number of limitations that Qt tries to solve with it's signal and slot architecture. The concept is that every object can emit signals. For example when a button is clicked it emits a “clicked()” signal. Signals does not do anything alone, but when connected to a slot the code in the slot will be executed every time the signal is emitted. In python every function is a slot. It's possible to connect one signal to multiple slots

		+	The signal and slot architecture is designed to simplify communication between objects. GUI programming is mostly event-driven and conventionally uses callbacks. The limitations of callbacks are partly resolved by the signal and slot architecture that Qt uses. The idea is that all objects can emit signals.
		+
		+	When a button is clicked, for example, it emits a “clicked()” signal. Signals do nothing alone, but once connected to a slot, the code in the slot will be executed whenever the signal is emitted.
		+
		+	In the Python programs, every function is a slot. It is possible to connect one signal to multiple slots, and to connect slots consecutively. For instance, one event activates its slot and related subsequent events trigger another signal and the code in its slot to be executed.

	==Prerequisites==		==Prerequisites==