After creating an item and setting it to as being editable:
item=QtGui.QTreeWidgetItem()
item.setFlags(item.flags() | QtCore.Qt.ItemIsEditable)
I want to reset all item's flags and set this item back to non-editable.
What would be correct syntax to achieve this?
You just have to perform the inverse operation you did as the Qt flags are bitwise.
item.setFlags(item.flags() & ~QtCore.Qt.ItemIsEditable)
The default value for flags is Qt::ItemIsSelectable | Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsDragEnabled
in case you want to set back the default behavior for the QTreeWidget.