new_contents: class RandomizedSet(object):
  
      def __init__(self):
          """
          Initialize your data structure here.
          """
          self.pos = dict()
          self.lst = []
  
      def insert(self, val):
          """
          Inserts a value to the set. Returns true if the set did not already contain the specified element.
          :type val: int
          :rtype: bool
          """
          if val not in self.pos:
              self.pos[val] = len(self.lst)
              self.lst.append(val)
              return True
          return False
  
      def remove(self, val):
          """
          Removes a value from the set. Returns true if the set contained the specified element.
          :type val: int
          :rtype: bool
          """
          if val in self.pos:
              idx = self.pos[val]
              self.pos[self.lst[-1]] = idx
              self.lst[idx] = self.lst[-1]
              self.lst.pop()
              self.pos.pop(val)
              return True
          return False
  
      def getRandom(self):
          """
          Get a random element from the set.
          :rtype: int
          """
          return random.choice(self.lst)
  
  
  # Your RandomizedSet object will be instantiated and called as such:
  # obj = RandomizedSet()
  # param_1 = obj.insert(val)
  # param_2 = obj.remove(val)
  # param_3 = obj.getRandom()
  
subject: Add py solution for 380. Insert Delete GetRandom O(1)