Qt for Python UsingQtProperties: Difference between revisions

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[[Category:Qt for Python]]


 
PySide2 provides a ''Property'' function which allows for declaring properties that simultaneously behave both as Qt and Python properties, and have their setters and getters defined as Python functions.
[[Category:PySide]]
[[Category:Snippets]]
 
'''English''' [[:Using_Qt_Properties_in_PySide_Korean|한국어]]
 
 
 
PySide provides a ''Property'' function which allows for declaring properties that simultaneously behave both as Qt and Python properties, and have their setters and getters defined as Python functions.


A short example illustrating defining and accessing a Qt property from Python is given below:
A short example illustrating defining and accessing a Qt property from Python is given below:


<code>
<syntaxhighlight lang="python" line='line'>
from PySide.QtCore import QObject, Property
from PySide2.QtCore import QObject, Property                                                      
                                                                                                   
class MyObject(QObject):                                                                           
    def __init__(self,startval=42):                                                               
        QObject.__init__(self)                                                                     
        self.ppval = startval                                                                     
                                                                                                   
    def readPP(self):                                                                                 
        return self.ppval                                                                             
                                                                                                   
    def setPP(self,val):                                                                               
        self.ppval = val                                                                               
                                                                                                   
    pp = Property(int, readPP, setPP)   
                                                             
obj = MyObject()                                                                                   
obj.pp = 47                                                                                       
print(obj.pp)
</syntaxhighlight>


class MyObject(QObject):
== Properties in QML expressions ==
def ''init''(self,startval=42):
QObject.''init''(self)
self.ppval = startval


def readPP(self):
If you are using properties of your objects in QML expressions, QML requires the property to be NOTIFYable or constant. If the value of the property changes over time, you should apply NOTIFYable using a simple signal:
return self.ppval


def setPP(self,val):
<syntaxhighlight lang="python" line='line'>
self.ppval = val
from PySide2.QtCore import QObject, Signal, Property


pp = Property(int, readPP, setPP)
class Person(QObject):
    def __init__(self, name):
        QObject.__init__(self)
        self._person_name = name


obj = MyObject()
    def _name(self):
obj.pp = 47
        return self._person_name
print (obj.pp)
</code>


The complete specification for PySide's property system is given in [http://web.archive.org/web/20120423210319/http://www.pyside.org/docs/pseps/psep-0103.html PSEP 103].
    @Signal
    def name_changed(self):
        pass


== Properties in QML expressions ==
    name = Property(str, _name, notify=name_changed)
</syntaxhighlight>


If you are using properties of your objects in QML expressions, QML requires the property to be NOTIFYable. This can be done using a simple signal:
You can use constant if your value is immutable. Use it as follows:


<code>
<syntaxhighlight lang="python" line='line'>
class Person(QtCore.QObject):
from PySide2.QtCore import QObject, Signal, Property
def ''init''(self, name):
QtCore.QObject.''init''(self)
self._person_name = name


def _name(self):
class Person(QObject):
return self._person_name
    def __init__(self, name):
        QObject.__init__(self)
        self._person_name = name


@QtCore.Signal
    def _name(self):
def name_changed(self): pass
        return self._person_name


name = QtCore.Property(unicode, _name, notify=name_changed)
    name = Property(str, _name, constant=True)
</code>
</syntaxhighlight>

Latest revision as of 16:48, 17 March 2020


PySide2 provides a Property function which allows for declaring properties that simultaneously behave both as Qt and Python properties, and have their setters and getters defined as Python functions.

A short example illustrating defining and accessing a Qt property from Python is given below:

from PySide2.QtCore import QObject, Property                                                        
                                                                                                    
class MyObject(QObject):                                                                            
    def __init__(self,startval=42):                                                                 
        QObject.__init__(self)                                                                      
        self.ppval = startval                                                                       
                                                                                                    
    def readPP(self):                                                                                   
        return self.ppval                                                                               
                                                                                                    
    def setPP(self,val):                                                                                
        self.ppval = val                                                                                
                                                                                                    
    pp = Property(int, readPP, setPP)     
                                                              
obj = MyObject()                                                                                    
obj.pp = 47                                                                                         
print(obj.pp)

Properties in QML expressions

If you are using properties of your objects in QML expressions, QML requires the property to be NOTIFYable or constant. If the value of the property changes over time, you should apply NOTIFYable using a simple signal:

from PySide2.QtCore import QObject, Signal, Property

class Person(QObject):
    def __init__(self, name):
        QObject.__init__(self)
        self._person_name = name

    def _name(self):
        return self._person_name

    @Signal
    def name_changed(self):
        pass

    name = Property(str, _name, notify=name_changed)

You can use constant if your value is immutable. Use it as follows:

from PySide2.QtCore import QObject, Signal, Property

class Person(QObject):
    def __init__(self, name):
        QObject.__init__(self)
        self._person_name = name

    def _name(self):
        return self._person_name

    name = Property(str, _name, constant=True)