Python栈的应用：编辑器的撤销操作

class Editor:
    def __init__(self):
        self.text = '' # 当前文本内容
        self.stack = [] # 撤销栈

    def insert(self, s):
        # 将文本内容压入栈顶
        self.stack.append(self.text)
        self.text += s

    def undo(self):
        if len(self.stack) > 0:
            # 从栈顶弹出最近一次的文本内容
            self.text = self.stack.pop()
        else:
            self.text = ''

    def get_text(self):
        return self.text

# 示例
editor = Editor()
editor.insert('pidan')
editor.insert('code')
editor.insert('.com')
print(editor.get_text()) # 输出：pidancode.com
editor.undo()
print(editor.get_text()) # 输出：pidancode
editor.undo()
print(editor.get_text()) # 输出：pidan
editor.undo()
print(editor.get_text()) # 输出：''（空字符串）