Python3.x 如何在输入正确的用户名和密码时添加按钮

您可以创建按钮，但将其设置为hidden，直到密码和用户名与所需的值匹配，方法是监听QLineEdit.textChanged信号，并在每次更改小部件内容时判断输入到两行编辑中的值.然后你可以拨打QPushButton.setHidden(False)来显示隐藏的按钮.

尽管我不建议以这种方式存储用户凭据...下面是一个例子:

import sys

from PySide6.QtWidgets import QApplication, QWidget, QLabel, QPushButton, QLineEdit, QVBoxLayout, QHBoxLayout, QFrame

from PySide6.QtGui import QFont

class Login(QWidget):

    def __init__(self):
        super().__init__()
        self.start_ui()

    def start_ui(self):
        self.generar_formulario()
        self.show()

    def generar_formulario(self):
        self.main_layout = QVBoxLayout()
        container_user = QFrame(self)
        hbox_layout_user = QHBoxLayout(container_user)
        user_label = QLabel('USUARIO: ', container_user)
        self.user_input = QLineEdit(container_user)
        font = QFont('Arial', 26)
        font.setBold(True)
        user_label.setFont(font)
        hbox_layout_user.addWidget(user_label)
        hbox_layout_user.addWidget(self.user_input)
        container_password = QFrame(self)
        hbox_layout_password = QHBoxLayout(container_password)
        password_label = QLabel('CONTRASEÑA: ', container_password)
        self.password_input = QLineEdit(container_password)
        self.password_input.setEchoMode(QLineEdit.Password)
        password_label.setFont(font)
        hbox_layout_password.addWidget(password_label)
        hbox_layout_password.addWidget(self.password_input)
        self.main_layout.addWidget(container_user)
        self.main_layout.addWidget(container_password)
        self.button_validation = QPushButton('Button', self)
        self.button_validation.setHidden(True)
        self.button_validation.clicked.connect(self.Validar_Credenciales)
        self.main_layout.addWidget(self.button_validation)
        self.resul_label = QLabel(self)
        #self.resul_label.setFont(QFont('Arial', 12))
        self.main_layout.addWidget(self.resul_label)
        container_user.move(50, 50)
        container_password.move(50, 150)
        self.button_validation.move(150, 250)
        self.resul_label.move(60, 350)
        self.usuario = "Pepe"
        self.password = "123"
        self.password_input.textChanged.connect(self.on_text_changed)
        self.user_input.textChanged.connect(self.on_text_changed)
        #self.setLayout(self.main_layout)

    def on_text_changed(self):
        usuario_get = self.user_input.text()
        contraseña_get = self.password_input.text()
        if usuario_get == self.usuario and contraseña_get == self.password:
            self.button_validation.setHidden(False)

    def Validar_Credenciales(self):
        usuario_get = self.user_input.text()
        contraseña_get = self.password_input.text()
        if usuario_get == self.usuario and contraseña_get == self.password:
            self.resul_label.setText(f"\tBienvenido {self.usuario},\n  aqui tenemos recomendaciones de videos")
            self.resul_label.adjustSize()
        else:
            self.resul_label.setText("Ingresa bien tu contraseña estupido")
            self.resul_label.adjustSize()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    login = Login()
    sys.exit(app.exec())