新增成比例的收縮量，如果收縮量為0時，所有的控制元件都分佈在介面的左邊

當收縮量不為0時

Stretch.py

"""
設定控制元件的伸縮量
"""

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

class Stretch(QWidget):
    def __init__(self):
        super(Stretch, self).__init__()
        self.setWindowTitle("設定控制元件的伸縮量")

        btn1 = QPushButton(self)
        btn2 
 
= QPushButton(self)
        btn3 = QPushButton(self)
        btn1.setText("按鈕1")
        btn2.setText("按鈕2")
        btn3.setText("按鈕3")

        layout = QHBoxLayout()
        layout.addStretch(1)
        layout.addWidget(btn1)

        layout.addStretch(2)
        layout.addWidget(btn2)

        layout.addStretch(
 
1)
        layout.addWidget(btn3)

        self.setLayout(layout)


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

    main = Stretch()
    main.show()

    sys.exit(app.exec_())

收縮量為0的時候

"""
設定控制元件的伸縮量
"""

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

 
class Stretch(QWidget):
    def __init__(self):
        super(Stretch, self).__init__()
        self.setWindowTitle("設定控制元件的伸縮量")
        self.resize(800, 100)
        btn1 = QPushButton(self)
        btn2 = QPushButton(self)
        btn3 = QPushButton(self)
        btn4 = QPushButton(self)
        btn5 = QPushButton(self)
        btn1.setText("按鈕1")
        btn2.setText("按鈕2")
        btn3.setText("按鈕3")
        btn4.setText("按鈕4")
        btn5.setText("按鈕5")

        layout = QHBoxLayout()

        layout.addStretch(0)
        layout.addWidget(btn1)
        layout.addWidget(btn2)
        layout.addWidget(btn3)
        layout.addWidget(btn4)
        layout.addWidget(btn5)

        btnOk = QPushButton(self)
        btnOk.setText("確定")
        btnCancel = QPushButton(self)
        btnCancel.setText("取消")
        layout.addStretch(1)
        layout.addWidget(btnOk)
        layout.addWidget(btnCancel)
        self.setLayout(layout)


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

    main = Stretch()
    main.show()

    sys.exit(app.exec_())