text: # Find the first occurrence of the target value in a given list, and return its index
  # 在给定列表中寻找特定值首次出现的位置，并返回其指针。
  
  # use for loop 
  def find_element(a_list, target_value):
       i = 0
       for each in a_list:
           # print each
           if each == target_value:
               return i
           i += 1
       return -1
      
  #use while loop    
  def find_element(a_list, target_value): 
      i = 0
      while a_list[i] != target_value:
          i += 1
          if i >= len(a_list):
              return -1
      return i
  