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Concatenate Two QFileSystemModels

In this post, my goal is to concatenate two QFileSystemModels to one and display them together. (Lots of updates has been made)
Context :
In my C drive , I created the folder MyFolder (https://drive.google.com/drive/folders/1M-b2o9CiohXOgvjoZrAnl0iRVQBD1sXY?usp=sharing) , in which there are some folders and some files, for the sake of producing the minimal reproducible example . Their structure is :
The following Python code using PyQt5 library (modified from How to display parent directory in tree view?) runs after importing necessary libraries:
#The purpose of the proxy model is to display the directory.
#This proxy model is copied here from the reference without modification.
class ProxyModel(QSortFilterProxyModel):
def __init__(self, parent=None):
super().__init__(parent)
self._root_path = ""
def filterAcceptsRow(self, source_row, source_parent):
source_model = self.sourceModel()
if self._root_path and isinstance(source_model, QFileSystemModel):
root_index = source_model.index(self._root_path).parent()
if root_index == source_parent:
index = source_model.index(source_row, 0, source_parent)
return index.data(QFileSystemModel.FilePathRole) == self._root_path
return True
#property
def root_path(self):
return self._root_path
#root_path.setter
def root_path(self, p):
self._root_path = p
self.invalidateFilter()
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.create_treeview()
self.setCentralWidget(self.treeView_1) #The line I will be talking about.
def create_treeview(self):
self.treeView_1 = QTreeView()
self.dirModel_1 = QFileSystemModel()
self.dirModel_1.setRootPath(QDir.rootPath())
path_1 = 'C:/MyFolder/SubFolder1' # Changing the path is sufficient to change the displayed directory
root_index_1 = self.dirModel_1.index(path_1).parent()
self.proxy_1 = ProxyModel(self.dirModel_1)
self.proxy_1.setSourceModel(self.dirModel_1)
self.proxy_1.root_path = path_1
self.treeView_1.setModel(self.proxy_1)
proxy_root_index_1 = self.proxy_1.mapFromSource(root_index_1)
self.treeView_1.setRootIndex(proxy_root_index_1)
self.treeView_2 = QTreeView()
self.dirModel_2 = QFileSystemModel()
self.dirModel_2.setRootPath(QDir.rootPath())
path_2 = 'C:/MyFolder'
root_index_2 = self.dirModel_2.index(path_2).parent()
self.proxy_2 = ProxyModel(self.dirModel_2)
self.proxy_2.setSourceModel(self.dirModel_2)
self.proxy_2.root_path = path_2
self.treeView_2.setModel(self.proxy_2)
proxy_root_index_2 = self.proxy_2.mapFromSource(root_index_2)
self.treeView_2.setRootIndex(proxy_root_index_2)
if __name__ == "__main__":
import sys
app = QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())
The line self.setCentralWidget(self.treeView_1) gives:
Changing self.setCentralWidget(self.treeView_1) to self.setCentralWidget(self.treeView_2) gives:
Objective:
My goal is to concatenate the two trees together. That is, when click run, the user should be able to see:
The order which they show up does not matter. All I care is that MyFolder and SubFolder1 show up as if they are completely independent items (even though in reality one is a subfolder of the other). I should remark that everything is static. That is, we are not trying to detect any changes on folders or files. The only time we ever need to peak at the existing folders and files will be when we click on run.
Update:
After several days of studying and trying, a major progress has been made. I thank musicamante for the hint of using QTreeWidget. The idea is, as said in comments, traverse through models and gradually move everything into one new QTreeWidget. To avoid freeze, my solution is to ask the QFileSystemModel to fetchMore whenever the user wants to see more (i.e. when the user wants to extend QTreeWidget).
The following code runs and almost solves my problem:
import os
from PyQt5.QtCore import*
from PyQt5.QtWidgets import*
from PyQt5 import QtTest
class To_Display_Folder(QSortFilterProxyModel):
def __init__(self, disables=False, parent=None):
super().__init__(parent)
#self.setFilterRegularExpression(r'^(.*\.dcm|[^.]+)$')
self._disables = bool(disables)
self._root_path = ""
def filterAcceptsRow(self, source_row, source_parent):
source_model = self.sourceModel()
#case 1 folder
if self._root_path and isinstance(source_model, QFileSystemModel):
root_index = source_model.index(self._root_path).parent()
if root_index == source_parent:
index = source_model.index(source_row, 0, source_parent)
return index.data(QFileSystemModel.FilePathRole) == self._root_path
return True
'''
#case 2 file
file_index = self.sourceModel().index(source_row, 0, source_parent)
if not self._disables:
return self.matchIndex(file_index)
return file_index.isValid()
'''
#property
def root_path(self):
return self._root_path
#root_path.setter
def root_path(self, p):
self._root_path = p
self.invalidateFilter()
def matchIndex(self, index):
return (self.sourceModel().isDir(index) or
super().filterAcceptsRow(index.row(), index.parent()))
def flags(self, index):
flags = super().flags(index)
if (self._disables and
not self.matchIndex(self.mapToSource(index))):
flags &= ~Qt.ItemIsEnabled
return flags
class Widget_Item_from_Proxy(QTreeWidgetItem):
def __init__(self, index_in_dirModel, parent = None):
super().__init__(parent)
self.setText(0, index_in_dirModel.data(QFileSystemModel.FileNameRole))
self.setText(1, index_in_dirModel.data(QFileSystemModel.FilePathRole))
if os.path.isfile(index_in_dirModel.data(QFileSystemModel.FilePathRole)):
self.setIcon(0,QApplication.style().standardIcon(QStyle.SP_FileIcon))
else:
self.setIcon(0,QApplication.style().standardIcon(QStyle.SP_DirIcon))
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
global treeWidget
treeWidget = QTreeWidget()
self.treeWidget = treeWidget
self.treeWidget.itemExpanded.connect(self.upon_expansion)
self.treeWidget.itemClicked.connect(self.tree_click)
#The following directories will be displayed on the tree.
self.add_path_to_tree_widget('C:/MyFolder')
self.add_path_to_tree_widget('C:/Users/r2d2w/OneDrive/Desktop')
self.add_path_to_tree_widget('C:/')
self.setCentralWidget(self.treeWidget)
def add_path_to_tree_widget(self,path):
dirModel = QFileSystemModel()
dirModel.setRootPath(QDir.rootPath())
dirModel.directoryLoaded.connect(lambda: self.once_loaded(path, dirModel))
def once_loaded(self, path, dirModel):
if dirModel.canFetchMore(dirModel.index(path)):
dirModel.fetchMore(dirModel.index(path))
return
root_index = dirModel.index(path).parent()
proxy = To_Display_Folder(disables = False, parent = dirModel)
proxy.setSourceModel(dirModel)
proxy.root_path = path
proxy_root_index = proxy.mapFromSource(root_index)
origin_in_proxy = proxy.index(0,0,parent = proxy_root_index)
root_item = Widget_Item_from_Proxy(
proxy.mapToSource(origin_in_proxy))
self.treeWidget.addTopLevelItem(root_item)
for row in range(0, proxy.rowCount(origin_in_proxy)):
proxy_index = proxy.index(row,0,parent = origin_in_proxy)
child = Widget_Item_from_Proxy(
proxy.mapToSource(proxy_index),
parent = self.treeWidget.topLevelItem(self.treeWidget.topLevelItemCount()-1))
dirModel.directoryLoaded.disconnect()
#pyqtSlot(QTreeWidgetItem)
def upon_expansion(self, treeitem):
for i in range(0, treeitem.childCount()):
if os.path.isdir(treeitem.child(i).text(1)):
self.add_child_path_to_tree_widget(treeitem.child(i))
def add_child_path_to_tree_widget(self,subfolder_item):
subfolder_path = subfolder_item.text(1)
dirModel = QFileSystemModel()
dirModel.setRootPath(QDir.rootPath())
dirModel.directoryLoaded.connect(lambda: self.child_once_loaded(subfolder_item, subfolder_path,dirModel))
def child_once_loaded(self, subfolder_item, subfolder_path, dirModel):
if dirModel.canFetchMore(dirModel.index(subfolder_path)):
dirModel.fetchMore(dirModel.index(subfolder_path))
return
root_index = dirModel.index(subfolder_path).parent()
proxy = To_Display_Folder(disables = False, parent = dirModel)
proxy.setSourceModel(dirModel)
proxy.root_path = subfolder_path
proxy_root_index = proxy.mapFromSource(root_index)
origin_in_proxy = proxy.index(0,0,parent = proxy_root_index)
root_item = Widget_Item_from_Proxy(
proxy.mapToSource(origin_in_proxy))
folder_item = subfolder_item.parent()
itemIndex = folder_item.indexOfChild(subfolder_item)
folder_item.removeChild(subfolder_item)
folder_item.insertChild(itemIndex, root_item)
for row in range(0, proxy.rowCount(origin_in_proxy)):
proxy_index = proxy.index(row,0,parent = origin_in_proxy)
child = Widget_Item_from_Proxy(
proxy.mapToSource(proxy_index),
parent = root_item)
dirModel.directoryLoaded.disconnect()
#pyqtSlot(QTreeWidgetItem)
def tree_click(self, item):
print(item.text(0))
print(item.text(1))
if __name__ == "__main__":
import sys
app = QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())
Since the bounty period is still not over, I will use the time to post two new questions:
Sometimes, especially when the line self.add_path_to_tree_widget('C:/') is present, the code does not give all directories when we click run. This problem is easily fixed by closing the window and clicking on run again. This problem occurs because the QFileSystemModel does not yet have enough time to traverse through the designated folder. If it has just a little bit more time, it will be able to. I wonder if there is a way to fix this programatically.
The function add_path_to_tree_widget is similar to add_child_path_to_tree_widget. The function once_loaded is similar to child_once_loaded. I wonder if there is a way to write these functions more succinctly.

While not impossible, it's quite difficult to create a unique and dynamic model that is able to access different QFileSystemModel structures.
An easier and simpler implementation, which would be more practical for static purposes, is to use a QTreeWidget and create items recursively.
class MultiBrowser(QTreeWidget):
def __init__(self, *pathList):
super().__init__()
self.iconProvider = QFileIconProvider()
self.setHeaderLabels(['Name'])
for path in pathList:
item = self.createFSItem(QFileInfo(path), self.invisibleRootItem())
self.expand(self.indexFromItem(item))
def createFSItem(self, info, parent):
item = QTreeWidgetItem(parent, [info.fileName()])
item.setIcon(0, self.iconProvider.icon(info))
if info.isDir():
infoList = QDir(info.absoluteFilePath()).entryInfoList(
filters=QDir.AllEntries | QDir.NoDotAndDotDot,
sort=QDir.DirsFirst
)
for childInfo in infoList:
self.createFSItem(childInfo, item)
return item
# ...
multiBrowser = MultiBrowser('path1', 'path2')
For obvious reasons, the depth of each path and their contents will freeze the UI from interaction until the whole structure has been crawled.
If you need a more dynamic approach, consider using the QFileSystemModel as a source for path crawling, along with its directoryLoaded signal, which will obviously require a more complex implementation.

Python class recording attributes without specifying self ?

I have a question regarding a Python class I use in Blender. Basically, I wonder how the class works because some attributes are recorded without me specifically writing self.value = something. Here's the code:
class DialogOperator(bpy.types.Operator):
bl_idname = "object.dialog_operator"
bl_label = "Save/Load animation"
saving = bpy.props.BoolProperty(name="Save ? Else load.")
path_to_anim = bpy.props.StringProperty(name="Path to folder")
anim_name = bpy.props.StringProperty(name="Animation name:")
# path_to_anim += "/home/mehdi/Blender/Scripts/"
def execute(self, context):
# print('This is execute with: Saving: {} Name:{}'.format(self.saving, self.path_to_anim))
if self.saving:
self.launch_save()
message = 'Animation {} saved at {}'.format(self.anim_name, self.path_to_anim)
else:
self.launch_load()
message = 'Animation {} loaded'.format(self.anim_name)
self.report({'INFO'}, message)
return {'FINISHED'}
def invoke(self, context, event):
wm = context.window_manager
return wm.invoke_props_dialog(self)
def launch_load(self):
full_path = self.path_to_anim + self.anim_name
target_armature = Humanoid(bpy.data.objects['Armature'])
load_all(full_path, target_armature, 'LastLoaded')
def launch_save(self):
full_path = self.path_to_anim + self.anim_name
source_armature = Humanoid(bpy.data.objects['Armature'])
curves = source_armature.get_curves()
save_all(curves, source_armature,full_path)
Now, how come saving, path_to_anim and anim_name are considered as attributes (I'm able to call them in execute() and launch()) even though I did not write self.saving = saving
Thanks !

This is because saving,path_to_anim and anim_name are class attributes. They are defined for the class and not for a particular instance. They are shared among the instances. Here is a link for further explanation class-instance-attributes-python

Button binding in Kivy Python

I am wondering how to get my code to work. I have a class wich creates a popup window with buttons. Each button should be bound to subclass. But it doesnt work. What´s wrong with my code?
class chooser:
def __init__(self):
None
def show(self,title,options=["NOTHING"],size=(.5,.5)):
self.bts = {}
self.response = False
self.content = FloatLayout()
self.content.pos_hint = {"y":0,"x":0}
# create buttons
pos_cntr = 0
for opt in options:
self.bts[pos_cntr] = Button(text=opt)
self.bts[pos_cntr].size_hint = 1,float(1)/float(len(options))
self.bts[pos_cntr].pos_hint = {"x":0,"y":pos_cntr}
self.bts[pos_cntr].bind(on_press=self.canceldia)
self.content.add_widget(self.bts[pos_cntr])
print "bound"
pos_cntr += float(1)/float(len(options))
self.pop = Popup(title=title,content=self.content,auto_dismiss=False)
self.pop.size_hint = size
self.pop.open()
def canceldia(self,instance):
print "closing"
self.response = instance.text
self.pop.dismiss()
def getresponse(self):
return self.response
I have imported all needed modules.
I execute it so:
c = chooser()
c.show("hello","world",["welcome","close","nothing","example"])
I have create a root widget. The popup works fine and all is created nice but the buttons are not bound. Please help me!

In your loop, you always reference self.bts[pos_cntr], so you override it in every iteration. How about this?
for idx, opt in enumerate(options):
self.bts[idx] = Button(text=opt)
self.bts[idx].size_hint = 1,float(1)/float(len(options))
self.bts[idx].pos_hint = {"x":0,"y":pos_cntr}
self.bts[idx].bind(on_press=self.canceldia)
self.content.add_widget(self.bts[idx])

(PyQt) Uncheck pushbutton from outside button's class?

A QPushButton is set 'asCheckable'. Whence toggled, a class bool is changed.
This altered bool allows a method in a different class to proceed, and upon completion of this outside method I need to return the button to its initial state, 'setChecked(False)'.
While I am able to return the class housed bool to its default state at the end of this external method, I am unable to externally access a method which un-clicks the button.
I assume its due to the arguments in the classes init, but these are necessary - and I'm wondering if there is another means to achieve the described workflow.
Related code snips below:
(command in question is distinguished at bottom of 'Class 2')
Class 1:
class shapeCSVeditor(QtGui.QDialog, QtGui.QWidget):
valueShare = []
rowOverride = False# <<=== equivalent to 'override' in 'Class 2'
def __init__(self, iface, fileName, editorType, parent=None):
super(shapeCSVeditor, self).__init__(parent)
self.iface = iface
self.editorType = editorType
self.fileName = filename
self.pushButtonSetBase = QtGui.QPushButton(self)
self.pushButtonSetBase.setText("Set Base Shape")
self.pushButtonSetBase.setCheckable(True)
self.pushButtonSetBase.toggled.connect(self.on_pushButtonSetBase_toggled)
self.layoutHorizontal.addWidget(self.pushButtonSetBase)
#some other things here...
#QtCore.pyqtSlot()
def on_pushButtonSetBase_toggled(self):
shapeCSVeditor.rowOverride = True
pass
def on_BaseRow_Changed(self):
self.pushButtonSetBase.setChecked(False)
return
Class 2:
class CSVModel(QtCore.QAbstractTableModel):
# Establish inital settings and branch processes
def __init__(self, iface, fileName, editorType, parent=None):
super(CSVModel,self).__init__()
self.propertiesFile = r'some file'
self.areaStressFile = r'some other file'
self.iface = iface
self.rows = []
self.editorType = editorType
self.loadCSV()
self.iface.mapCanvas().selectionChanged.connect(self.addRow)
# add rows to the TableView based on object selection(s) in Qgis.mapCanvas
def addRow(self):
override = shapeCSVeditor.rowOverride
selectedFeatures = selectedLayer.selectedFeatures()
if override:
for feature in selectedFeatures:
self.rows.pop(0)
feat_Attributes = []
feat_Attributes.extend([self.iface.activeLayer().name()+'_'+str(feature.id())])
feat_Attributes.extend(['',]*(len(self.header)-1))
self.beginResetModel()
self.rows.insert(0,feat_Attributes)
shapeCSVeditor.rowOverride = False
self.endResetModel()
shapeCSVeditor.on_BaseRow_Changed# <<<=== wrong-diddily!
break
PS - if parentheticals are added to the 'shapeCSVeditor()' 3 arguments are requisite as referenced in the Button class, and if parentheticals are added to 'on_BaseRow_Changed', the return is;
TypeError: unbound method on_BaseRow_Changed() must be called with
shapeCSVeditor instance as first argument (got nothing instead)

What you are doing is strange.
In python, the first argument of a class method is always the object itself.
So, in your:
def on_BaseRow_Changed(self):
self.pushButtonSetBase.setChecked(False)
# return => This return is useless
if you don't provide an object then you can't access the pushbutton.
You didn't gave us all the code but I think you should provide your addRow with the shapeCSVeditor object that you want to update:
def addRow(self, shapeCSVObj):
override = shapeCSVObj.rowOverride
if override:
for feature in selectedFeatures:
self.rows.pop(0)
feat_Attributes = []
feat_Attributes.extend([self.iface.activeLayer().name()+'_'+str(feature.id())])
feat_Attributes.extend(['',]*(len(self.header)-1))
self.beginResetModel()
self.rows.insert(0,feat_Attributes)
shapeCSVObj.rowOverride = False
self.endResetModel()
shapeCSVObj.on_BaseRow_Changed()
break
Somewhere you must have a shapeCSVeditor that is created. You should provide it to you outside class.
Hope this helps.

class shapeCSVeditor(QtGui.QDialog, QtGui.QWidget):
valueShare = []
rowOverride = False
def __init__(self, iface, fileName, editorType, parent=None):
super(shapeCSVeditor, self).__init__(parent)
self.iface = iface
self.editorType = editorType
self.fileName = fileName
self.tableView = QtGui.QTableView(self)
self.setWindowFlags(self.windowFlags() | QtCore.Qt.WindowStaysOnTopHint)
self.tableData = CSVModel(self,iface,fileName,editorType)
^^==not implementing 'self' (shapeCSVeditor object) was the problem!
self.tableView.setModel(self.tableData)
...
self.pushButtonSetBase = QtGui.QPushButton(self)
self.pushButtonSetBase.setText("Set Base Shape")
self.pushButtonSetBase.setCheckable(True)
self.pushButtonSetBase.clicked.connect(self.on_pushButtonSetBase_toggled)
...
#QtCore.pyqtSlot()
def on_pushButtonSetBase_toggled(self):
self.rowOverride = True
#QtCore.pyqtSlot()
def on_BaseRow_Changed(self):
self.rowOverride = False
self.pushButtonSetBase.setChecked(False)
///////////////////////////////////////////////////////////////////////////////////////
class CSVModel(QtCore.QAbstractTableModel):
def __init__(self, shapeCSVeditor, iface, fileName, editorType):
super(CSVModel,self).__init__()
self.propertiesFile = r'foo'
self.areaStressFile = r'bar'
self.tableView = shapeCSVeditor <<== proper passing of shapeCSVeditor object! (?)
self.iface = iface
self.rows = []
self.editorType = editorType
self.loadCSV()
self.iface.mapCanvas().selectionChanged.connect(self.addRow)
...
def addRow(self):
selectedFeatures = selectedLayer.selectedFeatures()
if self.tableView.rowOverride:
for feature in selectedFeatures:
self.rows.pop(0)
feat_Attributes = []
feat_Attributes.extend([self.iface.activeLayer().name()+'_'+str(feature.id())])
feat_Attributes.extend(['',]*(len(self.header)-1))
self.beginResetModel()
self.rows.insert(0,feat_Attributes)
self.endResetModel()
self.tableView.rowOverride = False
self.tableView.on_BaseRow_Changed()
Radical. Works for the current needs.
Now the question is if its proper to python 'standards'.
Quite new to writing, so its possible more needs fixed.
High thanks to Plouff for the clues.

Differentiating between signal sources in PySide

Is there trivial or elegant way to differentiate between many same-type signal sources in PySide/PyQt?
I am learning PySide. I have written simple application, which multiplies two numbers from two different QLineEdit() objects. Result is displayed in third QLineEdit.
Multiplier and multiplicand QLineEdit.textChanged() signals are connected to one method (TxtChanged). In this method i have to differentiate between signal sources. After some trials I figured out some workaround based upon placeholder text (4 lines below "is there another way?" comment in my code)
code:
import sys
from PySide import QtGui, QtCore
class myGUI(QtGui.QWidget):
def __init__(self, *args, **kwargs):
QtGui.QWidget.__init__(self, *args, **kwargs)
self.multiplier = 0
self.multiplicand = 0
self.myGUIInit()
def myGUIInit(self):
# input forms
a1_label = QtGui.QLabel("a1")
a1_edit = QtGui.QLineEdit()
a1_edit.setPlaceholderText("a1")
a2_label = QtGui.QLabel("a2")
a2_edit = QtGui.QLineEdit()
a2_edit.setPlaceholderText("a2")
# output form
a1a2_label = QtGui.QLabel("a1*a2")
self.a1a2_edit = QtGui.QLineEdit()
self.a1a2_edit.setReadOnly(True)
# forms events
a1_edit.textChanged.connect(self.TxtChanged)
a2_edit.textChanged.connect(self.TxtChanged)
# grid
grid = QtGui.QGridLayout()
grid.setSpacing(10)
grid.addWidget(a1_label,1,0)
grid.addWidget(a1_edit,1,1)
grid.addWidget(a2_label,2,0)
grid.addWidget(a2_edit,2,1)
grid.addWidget(a1a2_label,3,0)
grid.addWidget(self.a1a2_edit,3,1)
self.setLayout(grid)
self.setGeometry(100,100,200,200)
self.setWindowTitle("a*b")
self.show()
def TxtChanged(self,text):
sender = self.sender()
sender_text = sender.text()
if sender_text == '': sender_text = '0'
# is there another way?
if sender.placeholderText() == 'a1':
self.multiplicand = sender_text
else:
self.multiplier = sender_text
product = int(self.multiplier) * int(self.multiplicand)
print(self.multiplier,self.multiplicand,product)
self.a1a2_edit.setText(str(product))
def main():
app = QtGui.QApplication(sys.argv)
mainWindow = myGUI()
sys.exit(app.exec_())
main()
best regards,
ostrzysz

You can use the functools.partial function - and therefore connect your signals to straight to your method/function but rather to a python object which will automatically call your function with some extra data you pass it:
from functools import partial
...
....
a1_edit.textChanged.connect(partial(self.TxtChanged, a1_edit))
a2_edit.textChanged.connect(partial(self.TxtChanged, a2_edit))
...
def TxtChanged(self,sender, text):
# and here you have the "sender" parameter as it was filled in the call to "partial"
...
partials is part of the stdlib, and is very readable, but one can always use lambda instead of partial for the same effect -
a1_edit.textChanged.connect(lambda text: self.TxtChanged(a1_edit, text))
In this way the object yielded by the lambda expression will be a temporary function that will use the values for "self" and "a1_edit" from the current local variables (at the time the button is clicked), and the variable named "text" will be supplied by Pyside's callback.

One thing that bugs me most in your code is that you are using placeholderText to differentiate. QObjects has another property called objectName that is more suitable for your task. And, you don't need to use sender.text() to get the text of QLineEdit. textChanged already sends it, so you will have it in your text parameter.
Also, using a dictionary instead of two separate variables (multiplier and multiplicand) will simplify your code further.
Here is the changed code:
class myGUI(QtGui.QWidget):
def __init__(self, *args, **kwargs):
QtGui.QWidget.__init__(self, *args, **kwargs)
self.data = {"multiplier": 0,
"multiplicand": 0}
self.myGUIInit()
def myGUIInit(self):
a1_label = QtGui.QLabel("a1")
a1_edit = QtGui.QLineEdit()
a1_edit.setObjectName("multiplicand")
a2_label = QtGui.QLabel("a2")
a2_edit = QtGui.QLineEdit()
a2_edit.setObjectName("multiplier")
# skipped the rest because same
def TxtChanged(self, text):
sender = self.sender()
# casting to int while assigning seems logical.
self.data[sender.objectName()] = int(text)
product = self.data["multiplier"] * self.data["multiplicand"]
print(self.data["multiplier"], self.data["multiplicand"], product)
self.a1a2_edit.setText(str(product))

Although #jsbueno and #Avaris answered your direct question about signal sources, I wouldn't relay on this sources in your concrete case. You can make instance members a1_edit and a2_edit:
...
self.a1_edit = QtGui.QLineEdit()
...
self.a2_edit = QtGui.QLineEdit()
...
It will simplify your TxtChanged function:
def TxtChanged(self,text):
try:
multiplier = int(self.a1_edit.text())
multiplicand = int(self.a2_edit.text())
except ValueError:
self.a1a2_edit.setText('Enter two numbers')
return
product = multiplier * multiplicand
print(multiplier, multiplicand, product)
self.a1a2_edit.setText(str(product))
Also, instead of handling ValueError exception, you can use QIntValidator for input controls:
self.int_validator = QtGui.QIntValidator()
self.a1_edit.setValidator(self.int_validator)
self.a2_edit.setValidator(self.int_validator)