Custom styled tabs in QT

custom_tabs.py

import sys
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPixmap
from PyQt5.QtWidgets import (QApplication, QDialog, QWidget,
                             QLabel, QLineEdit, QHBoxLayout, QVBoxLayout, QPushButton, 
                             QButtonGroup, QStackedLayout)


class Dialog(QDialog):

    def __init__(self):
        super(Dialog, self).__init__()
        main_layout = QVBoxLayout()
        # image header
        img = QLabel()
        img.setPixmap(QPixmap('waves.png'))
        
        # custom tabs
        hbox = QHBoxLayout()
        self.new_project_button = QPushButton('Sign In')
        self.new_project_button.setObjectName('CustomTab')
        self.new_project_button.setCheckable(True)
        self.new_project_button.setChecked(True)    
        
        self.load_project_button = QPushButton('Register')
        self.load_project_button.setObjectName('CustomTab')
        self.load_project_button.setCheckable(True)
        
        # The button group box ensures exclusive tab selection
        self.group = QButtonGroup()
        self.group.addButton(self.new_project_button, 0)
        self.group.addButton(self.load_project_button, 1)
        hbox.addWidget(self.new_project_button)
        hbox.addWidget(self.load_project_button)
        hbox.setSpacing(0)

        # create stacked layout 
        self.stack = QStackedLayout()
        self.stack1 = QWidget()
        self.stack2 = QWidget()
        self.stack1.setContentsMargins(30, 0, 30, 0)
        self.stack2.setContentsMargins(30, 0, 30, 0)
        self.stack.addWidget(self.stack1)
        self.stack.addWidget(self.stack2)
        self.group.buttonClicked[int].connect(self.stack.setCurrentIndex)

        # Add content to stack layout  
        self.createSignInForm()
        self.createSignUpForm()

        main_layout.setContentsMargins(0,0,0,0)     
        main_layout.addWidget(img)
        main_layout.addLayout(hbox)
        main_layout.addLayout(self.stack)
        self.setLayout(main_layout)

        self.setWindowFlags(Qt.FramelessWindowHint)
        self.setMinimumSize(640, 480)

    def createSignInForm(self):
       
        layout = QVBoxLayout()
        layout.addStretch(1)
        layout.addWidget(QLabel("Username:"))
        textbox = QLineEdit()
        layout.addWidget(textbox)
        layout.addStretch(1)

        layout.addWidget(QLabel("Password:"))
        textbox = QLineEdit()
        textbox.setEchoMode(QLineEdit.Password)
        layout.addWidget(textbox)
        layout.addStretch(1)
        
        hbox = QHBoxLayout()
        button = QPushButton('Login')
        hbox.addWidget(button)
        hbox.addStretch(1)
        layout.addLayout(hbox)
        layout.addStretch(1)

        self.stack1.setLayout(layout)

    def createSignUpForm(self):
       
        layout = QVBoxLayout()
        layout.addStretch(1)
        layout.addWidget(QLabel("Email:"))
        textbox = QLineEdit()
        layout.addWidget(textbox)
        layout.addStretch(1)

        layout.addWidget(QLabel("Password:"))
        textbox = QLineEdit()
        textbox.setEchoMode(QLineEdit.Password)
        layout.addWidget(textbox)
        layout.addStretch(1)
        
        hbox = QHBoxLayout()
        button = QPushButton('Sign up')
        hbox.addWidget(button)
        hbox.addStretch(1)
        layout.addLayout(hbox)
        layout.addStretch(1)

        self.stack2.setLayout(layout)

if __name__ == '__main__':

    style=''
    with open('style.qss', 'rt') as sytlesheet:
        style = sytlesheet.read()

    app = QApplication(sys.argv)
    app.setStyleSheet(style)
    dialog = Dialog()
sys.exit(dialog.exec_())

style.qss

* {
  font-family:"Helvetica Neue", Helvetica, Arial;
  font-size: 12px;
}

QLineEdit{
  padding:5px;
}

QPushButton {
    padding: 10px 15px;
}
 
#CustomTab{
    padding:10px 5px;
    font-size: 13px;
    margin:0;
    Font Weight: 300;
    border-top: 1px transparent;
    border-bottom: 2px solid #ddd;
    border-right: 1px transparent;
    border-left: 1px transparent;
}

#CustomTab:checked,
#CustomTab:checked:hover,
#CustomTab:checked:focus,
#CustomTab:checked:pressed{
    border-bottom: 2px solid DodgerBlue;
}