title: Error lambda missing 1 required positional argument when using with QPushButton
body: <p>This is entire my code:</p>
  <pre class="lang-py prettyprint-override"><code>import sys
  
  from PySide2.QtCore import Qt
  from PySide2.QtWidgets import (
      QApplication,
      QHBoxLayout,
      QLabel,
      QMainWindow,
      QPushButton,
      QVBoxLayout,
      QWidget,
  )
  
  class MainWindow(QMainWindow):
      def __init__(self):
          super().__init__()
  
          v = QVBoxLayout()
          h = QHBoxLayout()
  
          for a in range(10):
              button = QPushButton(str(a))
              button.clicked.connect(lambda checked, a=a: self.button_clicked(a)) # error here
  
              h.addWidget(button)
  
          v.addLayout(h)
  
          self.label = QLabel(&quot;&quot;)
          v.addWidget(self.label)
          
          w = QWidget()
          w.setLayout(v)
  
          self.setCentralWidget(w)
  
      def button_clicked(self, n):
          self.label.setText(str(n))
  
  app = QApplication(sys.argv)
  window = MainWindow()
  window.show()
  app.exec_()
  </code></pre>
  <p>When I run this code, I get a window like this:<img src="https://i.stack.imgur.com/lxG9B.png" alt="image here" /></p>
  <p><br>Below the buttons, there is a QLabel, and I want when I click on any button, the button's label will refer to this QLabel, but I get a bunch of confusing errors in the terminal. What's wrong with my code, help me, thanks.</p>