populate combobox editable username and line edit password from sqlite3

Question

I have 1 combobox editable username and 1 line edit password i want load user list from database sqlite3 to combobox. After load list i want action on itemlist combobox get

Answer 1

Assuming that the table is called "user" then you can use the userData to save the information and set it in the QLineEdit when the currentIndex of the QComboBox changes:

import os
import sqlite3
import sys

from PyQt5 import QtWidgets, QtSql


class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.username_combo = QtWidgets.QComboBox()
        self.password_lineedit = QtWidgets.QLineEdit()

        button_login = QtWidgets.QPushButton(self.tr("Login"))

        lay = QtWidgets.QFormLayout(self)
        lay.addRow(self.tr("Username:"), self.username_combo)
        lay.addRow(self.tr("Password:"), self.password_lineedit)
        lay.addRow(button_login)

        self.username_combo.currentIndexChanged.connect(self.update_password)

        self.load_usernames()

    def load_usernames(self):
        current_dir = os.path.dirname(os.path.realpath(__file__))
        db_path = os.path.join(current_dir, "testdb.db")

        self.username_combo.clear()
        with sqlite3.connect(db_path) as conn:
            cursor = conn.execute("SELECT DISTINCT username, password FROM User")
            for result in cursor.fetchall():
                username, password = result
                self.username_combo.addItem(username, password)

    def update_password(self):
        self.password_lineedit.setText(self.username_combo.currentData())


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())

Another possible solution is to use QSqlQueryModel with QDataWidgetMapper:

import os
import sys

from PyQt5 import QtWidgets, QtSql


def create_connection():
    current_dir = os.path.dirname(os.path.realpath(__file__))
    db_path = os.path.join(current_dir, "testdb.db")

    db = QtSql.QSqlDatabase.addDatabase("QSQLITE")
    db.setDatabaseName(db_path)
    if not db.open():
        print("error: {}".format(db.lastError().text()))
        return False
    return True


class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.username_combo = QtWidgets.QComboBox()
        self.password_lineedit = QtWidgets.QLineEdit()

        button_login = QtWidgets.QPushButton(self.tr("Login"))

        lay = QtWidgets.QFormLayout(self)
        lay.addRow(self.tr("Username:"), self.username_combo)
        lay.addRow(self.tr("Password:"), self.password_lineedit)
        lay.addRow(button_login)
        self.load_data()

    def load_data(self):
        self.model = QtSql.QSqlQueryModel()
        self.model.setQuery("""SELECT DISTINCT username, password FROM User""")
        self.mapper = QtWidgets.QDataWidgetMapper()
        self.mapper.setModel(self.model)
        self.mapper.addMapping(self.password_lineedit, 1)
        self.username_combo.currentIndexChanged.connect(self.mapper.setCurrentIndex)
        self.username_combo.setModel(self.model)


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)

    if not create_connection():
        sys.exit(-1)

    w = Widget()
    w.show()

    sys.exit(app.exec_())