怎么實現(xiàn)PyQt5控件字體樣式等設(shè)置

import sys

from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QFrame
from PyQt5.QtWidgets import QLabel
from PyQt5.QtWidgets import QWidget
from PyQt5.QtWidgets import QLineEdit
from PyQt5.QtWidgets import QTextEdit
from PyQt5.QtWidgets import QSizePolicy
from PyQt5.QtWidgets import QMainWindow
from PyQt5.QtWidgets import QPushButton
from PyQt5.QtWidgets import QGridLayout
from PyQt5.QtWidgets import QApplication




from View import interface

class MainWindow(QMainWindow):

  def __init__(self):
    super(MainWindow,self).__init__(None)
    self.setWindowTitle("對金屬腐蝕性試驗儀")
    self.initUI()

  def initUI(self):
    layout = QGridLayout()
    layout.setSpacing(10)
    self.loginLabel = QLabel("用戶名：")
    self.loginLabel.setAlignment(Qt.AlignRight)
    self.loginLabel.setStyleSheet("color:rgb(20,20,20,255);font-size:16px;font-weight:bold:text")
    self.loginTxt = QLineEdit()
    self.loginTxt.setText("admin")
    self.loginTxt.setPlaceholderText("User Name")
    self.loginTxt.setClearButtonEnabled(True)
    self.pwdLabel = QLabel("密碼：")
    self.pwdLabel.setAlignment(Qt.AlignRight)
    self.pwdTxt = QLineEdit()
    self.pwdTxt.setContextMenuPolicy(Qt.NoContextMenu) #禁止復(fù)制粘貼
    self.pwdTxt.setPlaceholderText("Password")
    self.pwdTxt.setText("admin")
    self.pwdTxt.setEchoMode(QLineEdit.Password)
    self.pwdTxt.setClearButtonEnabled(True)
    self.registeredBtn = QPushButton("注冊")
    self.loginBtn = QPushButton("登陸")

    self.headLabel = QLabel("用戶登陸")
    self.headLabel.resize(300,30)
    self.headLabel.setAlignment(Qt.AlignCenter)
    self.headLabel.setStyleSheet("color:rgb(10,10,10,255);font-size:25px;font-weight:bold;font-family:Roman times;")

    self.headLabel.setSizePolicy(QSizePolicy.Expanding,QSizePolicy.Expanding)
    layout.addWidget(self.headLabel,0,0,1,2)
    policy = self.headLabel.sizePolicy()
    print(policy.verticalPolicy())
    policy.setVerticalPolicy(1)
    print(policy.verticalPolicy())
    # policy.setVerticalPolicy(1)
    layout.addWidget(self.loginLabel,1,0)
    layout.addWidget(self.loginTxt,1,1)
    layout.addWidget(self.pwdLabel,2,0)
    layout.addWidget(self.pwdTxt,2,1)
    layout.addWidget(self.registeredBtn,3,0)
    layout.addWidget(self.loginBtn,3,1)

    frame = QFrame(self)
    frame.setLayout(layout)
    self.setCentralWidget(frame)
    self.resize(300,150)

if __name__ == '__main__':
  app = QApplication(sys.argv)
  mainWindow = MainWindow()
  mainWindow.show()
  mainWindow.activateWindow()
  mainWindow.raise_()
  app.exec_()
  del mainWindow
  del app