[PyQt] Help PyQt5

[Sabroso Rico]

Greetings to all I have, this function serves to validate if the user and e exist in the database and can log your look with them, but not working please help me omo can do well?
##################################################################
    def entrar(self):
        usa = self.txa.text()
        if len(usa) == 0:
            self.txt.setText('Datos vacios')
        else:
            # self.txt.setText('Valido')
            sql = ("SELECT id FROM usuarios WHERE nombre = '%s' AND correo = '%s' LIMIT 1", str(usa))
            datos = consultas(sql)
            if  len(datos)  == 0:
                self.txt.setText('Datos incorrectos ??')
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