use__qss__qt_style_sheet__local.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

__author__ = 'ipetrash'


from PyQt5.Qt import QApplication, QLabel, QVBoxLayout, QWidget

app = QApplication([])

label_1 = QLabel()
label_1.setText('Hello World!!!')
label_1.setStyleSheet("""
    font: bold italic;
    color: green;
    background-color: black;
""")

label_2 = QLabel()
label_2.setText('nothing...')

layout = QVBoxLayout()
layout.addWidget(label_1)
layout.addWidget(label_2)

mw = QWidget()
mw.setLayout(layout)
mw.show()

app.exec()