Question

I’m trying to convert a QVariant to a QSize.

from PyQt4.QtCore import (                                                     
    QVariant,                                                                  
    QSize,                                                                      
    )                                                                          

s = QSize(4,3)                                                                 
x = QVariant(s)                                                                

#Check, and hopefully do conversion                                            
print x.canConvert(QVariant.Size) #True                                           
print x.convert(QVariant.Size)    #True                                           
print type(x)                     #<class 'PyQt4.QtCore.QVariant'>...why??                
print type(x.toSize())            #<class 'PyQt4.QtCore.QSize'>

Why do I have to do x.toSize for the type of x to be QSize? I expected x.convert() would make x an instance of QSize.

This wasn’t of much help to me… http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qvariant.html#convert
…because it says that convert() “casts the variant to the requested type…”

Thanks for the help!

Answer 1

You have misunderstood the purpose of QVariant.convert.

It converts the type of the variant value, not the QVariant itself.

To demonstrate:

>>> from PyQt4.QtCore import QVariant
>>> v = QVariant(100)
>>> v.typeName()
'int'
>>> v.convert(QVariant.String)
True
>>> v.typeName()
'QString'

The to*() functions return the variant value converted to the requested type (if possible), but do not change the current type of the QVariant itself:

>>> v.toInt()
(100, True)
>>> v.typeName()
'QString'