通過構建垂直佈局，然後將上半部和需要放在下方的按鈕，設定收縮量，一個收縮量為0， 按鈕的收縮量為1

RightBottomButton.py

"""
讓按鈕永遠在視窗右下角
"""

import sys, math
from PyQt5.QtWidgets import *
from PyQt5.QtCore import Qt

class RightBottomButton(QWidget):
    def __init__(self):
        super(RightBottomButton, self).__init__()
        self.setWindowTitle(
 
"讓按鈕永遠在右下角")
        self.resize(400, 300)

        okButton = QPushButton("確定")
        cancelButton = QPushButton("取消")
        hbox = QHBoxLayout()
        hbox.addStretch(1)
        hbox.addWidget(okButton)
        hbox.addWidget(cancelButton)

        vbox = QVBoxLayout()
        btn1 = QPushButton("
 
按鈕1")
        btn2 = QPushButton("按鈕2")
        btn3 = QPushButton("按鈕3")

        vbox.addStretch(0)
        vbox.addWidget(btn1)
        vbox.addWidget(btn2)
        vbox.addWidget(btn3)
        vbox.addStretch(1)
        vbox.addLayout(hbox)

        self.setLayout(vbox)


if __name__ == "__main__
 
":
    app = QApplication(sys.argv)

    main = RightBottomButton()
    main.show()

    sys.exit(app.exec_())