python command to "get" the text from the Qt Designer fields and save it in sqlite

If your input field is a QtWidget.QLineEdit , you get the text with the call to .text() method.

If it is a field of type QtWidgets.QTextEdit , you first get a reference to the QTextDocument associated, and then you can have all the content being edited with a call to .toPlainText() method

conteudo = widget.document().toPlainText()

"hello world" type app to always display the last line entered in the edit area:

from PyQt5 import QtWidgets
import sys


def update(document, line):
    text = document.toPlainText()
    last_line = text.split("\n")[-1]
    line.setText(last_line)


def main():
    app = QtWidgets.QApplication(sys.argv)
    window = QtWidgets.QWidget()
    manager = QtWidgets.QGridLayout(window)

    area = QtWidgets.QTextEdit()
    line = QtWidgets.QLineEdit()

    document = area.document()

    document.contentsChange.connect(lambda: update(document, line))

    manager.addWidget(area, 0, 0)
    manager.addWidget(line, 1, 0)

    window.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

About this program: the document.contentsChange.connect(lambda: update(document, line)) line connects the text change signal with an anonymous function defined in the same place: lambda: update(document, line) - because the Qt signals do not send other parameters together. As in callback update I want to have access to the document and the other widget, lambda is called without parameters, and calls update passing the variables that I want to have access to in the other function as parameters.