how to make multi window using pyqt5 - pyqt5

Question

everybody!
Here's what I'm trying to do:
First, I created a file called basic.ui with a pushbutton.
Press the pushbutton to set the path and select the picture file in the set path to want the picture to appear in a new window(another window).
Let me tell you about the part where I am having difficulty.
The command to blow up the file is executed. Selecting the file causes an error.
I wonder what the cause is the problem.
How do I get the picture to appear in a new window(another window) after pressing the button?????
MainActivity.python
import sys
try:
from PyQt5.QtCore import Qt, QT_VERSION_STR
from PyQt5.QtGui import QImage
from PyQt5.QtWidgets import QApplication, QFileDialog
except ImportError:
try:
from PyQt4.QtCore import Qt, QT_VERSION_STR
from PyQt4.QtGui import QImage, QApplication, QFileDialog
except ImportError:
raise ImportError("Requires PyQt5 or PyQt4.")
from QtImageViewer import QtImageViewer
from PyQt5 import QtWidgets
from PyQt5 import QtGui
from PyQt5 import uic
from PyQt5.QtCore import pyqtSlot
class From(QtWidgets.QDialog):
def __init__(self, parent=None):
QtWidgets.QDialog.__init__(self, parent)
self.ui=uic.loadUi("basic.ui",self)
self.ui.show()
#pyqtSlot()
def add_number(self):
app = QApplication(sys.argv)
viewer=QtImageViewer()
fileName, dummy = QFileDialog.getOpenFileName(None, "Open image file...")
image = QImage(fileName)
viewer.setImage(image)
viewer.show()
sys.exit(app.exec_())
if __name__=='__main__':
app=QtWidgets.QApplication(sys.argv)
w=From()
sys.exit(app.exec())

Answer 1

Signals & Slots
Signals and slots are used for communication between objects. The signals and slots mechanism is a central feature of Qt and probably the part that differs most from the features provided by other frameworks. Signals and slots are made possible by Qt's meta-object system.
http://doc.qt.io/qt-5/signalsandslots.html
Try it:
import sys
from os import getcwd
from PyQt5 import QtWidgets
from PyQt5 import QtGui
from PyQt5 import uic
from PyQt5.QtCore import Qt, pyqtSlot
class From(QtWidgets.QDialog):
def __init__(self, parent=None):
super(From, self).__init__(parent)
self.ui=uic.loadUi("basic.ui",self)
self.ui.pushButton.clicked.connect(self.add_number) # +++
# ^^^^^^^^^^ vvvvvvvvvv
# <widget class="QPushButton" name="pushButton"> <---> "basic.ui"
self.ui.labelImagen = QtWidgets.QLabel()
self.ui.show()
#pyqtSlot()
def add_number(self):
fileName, dummy = QtWidgets.QFileDialog.getOpenFileName(
self, "Open image file...", getcwd(),
"Image (*.png *.jpg)",
options=QtWidgets.QFileDialog.Options())
if fileName:
pix = QtGui.QPixmap(fileName)
self.ui.labelImagen.setPixmap(pix)
self.ui.labelImagen.show()
if __name__=='__main__':
app=QtWidgets.QApplication(sys.argv)
w=From()
sys.exit(app.exec())