import sys
from PyQt5.QtWidgets import QApplication ,QWidget ,QVBoxLayout , QPushButton
class Winform(QWidget):
  def __init__(self,parent=None):
    super(Winform,self).__init__(parent)
    self.setWindowTitle("垂直布局管理例子") 
    self.resize(330, 150) 
    # 垂直布局按照从上到下的顺序进行添加按钮部件。
    vlayout = QVBoxLayout()
    vlayout.addWidget( QPushButton(str(1)))
    vlayout.addWidget( QPushButton(str(2)))
    vlayout.addWidget( QPushButton(str(3)))
    vlayout.addWidget( QPushButton(str(4)))
    vlayout.addWidget( QPushButton(str(5)))
    self.setLayout(vlayout)  
if __name__ == "__main__": 
    app = QApplication(sys.argv) 
    form = Winform()
    form.show()
    sys.exit(app.exec_())

from PyQt5.QtWidgets import QApplication ,QWidget, QVBoxLayout , QHBoxLayout ,QPushButton
import sys 
class WindowDemo(QWidget): 
  def __init__(self ): 
    super().__init__()
    btn1 = QPushButton(self)
    btn2 = QPushButton(self)
    btn3 = QPushButton(self)   
    btn1.setText('button 1')
    btn2.setText('button 2')
    btn3.setText('button 3')
    hbox = QHBoxLayout()
    # 设置伸缩量为1
    hbox.addStretch(1)
    hbox.addWidget( btn1 )
    # 设置伸缩量为1
    hbox.addStretch(1)
    hbox.addWidget( btn2 )
    # 设置伸缩量为1
    hbox.addStretch(1)
    hbox.addWidget( btn3 )
    # 设置伸缩量为1
    hbox.addStretch(1 )    
    self.setLayout(hbox)
    self.setWindowTitle("addStretch 例子")
if __name__ == "__main__": 
  app = QApplication(sys.argv) 
  win = WindowDemo() 
  win.show() 
  sys.exit(app.exec_())

import sys
from PyQt5.QtWidgets import QApplication ,QWidget ,QHBoxLayout , QPushButton
class Winform(QWidget):
  def __init__(self,parent=None):
    super(Winform,self).__init__(parent)
    self.setWindowTitle("水平布局管理例子") 
    self.resize(800, 50)
    # 水平布局按照从左到右的顺序进行添加按钮部件。
    hlayout = QHBoxLayout() 
    # 添加伸缩   
    hlayout.addStretch(0)
    hlayout.addWidget( QPushButton(str(1)) )
    hlayout.addWidget( QPushButton(str(2)) )
    hlayout.addWidget( QPushButton(str(3)))
    hlayout.addWidget( QPushButton(str(4)) )    
    hlayout.addWidget( QPushButton(str(5)) )  
    # 添加伸缩   
    #hlayout.addStretch(1)
    self.setLayout(hlayout)  
if __name__ == "__main__": 
  app = QApplication(sys.argv) 
  form = Winform()
  form.show()
  sys.exit(app.exec_())