How to access from parent method to child object in PyQt5? - pyqt5

Question

I have a button in widget widget which is a central widget of MyApp class, which inherits from QMainWindow. I have connected widget's button to MyApp's method called logic. This is fine, because if I write a method in my main class MyApp(QMainWindow):
def logic(self):
sender = self.sender()
print(sender)
... and click the button I get a message:
PyQt5.QtWidgets.QPushButton object at 0x7ff92e19eaf8
My question is how can I from MyApp's method called logic access to its child object like MyApp.widget.saltLine which is a QLineEdit object? I need to read that line.
class MyApp(QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.initui()
def initui(self):
self.setMinimumSize(500, 150)
# create central widget
widget = QWidget()
# lines for entering data
widget.saltLabel = QLabel("Salt:")
widget.hashSunkenLabel = QLabel()
widget.passwordLine = QLineEdit()
widget.resultButton = QPushButton("&Calculate", self)
# set layout
grid = QGridLayout()
grid.addWidget(widget.saltLabel, 0, 0)
grid.addWidget(widget.passwordLine, 1, 0)
grid.addWidget(widget.hashSunkenLabel, 2, 0)
grid.addWidget(widget.resultButton, 2, 1)
# set widget a grid layout and set widget
# as central widget of QMainWindows
widget.setLayout(grid)
self.setCentralWidget(widget)
# don't know how should this look like
widget.resultButton.clicked.connect(self.logic)
def logic(self):
salt = self.saltLine.text()
password = self.passwordLine.text()
resulting_hash = crypt.crypt(password, salt)
self.hashSunkenLabel.setText(resulting_hash)
Or am I definig centralwidget widget wrong? If I do it without a central widget it works fine:
#!/usr/bin/env python3
import sys
import crypt
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import (QMainWindow, QLabel, QLineEdit, QPushButton,
QWidget, QApplication, QSystemTrayIcon, QFrame, QGridLayout)
class MyApp(QWidget):
def __init__(self, parent=None):
super().__init__(parent)
self.saltLabel = QLabel("Salt:")
self.saltLine = QLineEdit()
self.saltLine.setPlaceholderText("e.g. $6$xxxxxxxx")
self.passwordLabel = QLabel("Password:")
self.passwordLine = QLineEdit()
self.hashLabel = QLabel("Hash:")
self.hashSunkenLabel = QLabel()
# widget.hashSunkenLabel.setFrameStyle(QFrame.Box | QFrame.Sunken)
self.hashSunkenLabel.setFrameShadow(QFrame.Sunken)
self.resultButton = QPushButton("&Calculate", self)
self.resultButton.setMaximumSize(100, 50)
self.initui()
def initui(self):
# main window size, title and icon
self.setGeometry(300, 300, 500, 150)
self.setWindowTitle("Password hash calculator | Linux")
# set layout
grid = QGridLayout()
grid.addWidget(self.passwordLabel, 0, 0)
grid.addWidget(self.passwordLine, 0, 1)
grid.addWidget(self.saltLabel, 1, 0)
grid.addWidget(self.saltLine, 1, 1)
grid.addWidget(self.resultButton, 2, 1)
grid.addWidget(self.hashLabel, 3, 0)
grid.addWidget(self.hashSunkenLabel, 3, 1)
self.setLayout(grid)
self.resultButton.clicked.connect(self.logic)
def logic(self):
"""
Calculates hash from salt and password
"""
salt = self.saltLine.text()
password = self.passwordLine.text()
resulting_hash = crypt.crypt(password, salt)
self.hashSunkenLabel.setText(resulting_hash)
# sender = self.sender()
# print(sender)
# print(dir(MyApp))
def main():
app = QApplication(sys.argv)
instance = MyApp()
instance.show()
sys.exit(app.exec_())
if __name__ == "__main__":
main()