old_contents: # You're given strings J representing the types of stones that are jewels, 
  # and S representing the stones you have.  Each character in S is a type of 
  # stone you have.  You want to know how many of the stones you have are also 
  # jewels.
  
  # The letters in J are guaranteed distinct, and all characters in J and S are 
  # letters. Letters are case sensitive, so "a" is considered a different type of 
  # stone from "A".
  
  # Example 1:
  
  # Input: J = "aA", S = "aAAbbbb"
  # Output: 3
  # Example 2:
  
  # Input: J = "z", S = "ZZ"
  # Output: 0
  
  # Note:
  # S and J will consist of letters and have length at most 50.
  # The characters in J are distinct.
  
  class Solution:
      def numJewelsInStones(self, J, S):
          """
          :type J: str
          :type S: str
          :rtype: int
          """
          jewels = set()
          for char in J:
              jewels.add(char)
          
          result = 0
          for stone in S:
              if stone in jewels:
                  result += 1
          
          return result
new_contents: # You're given strings J representing the types of stones that are jewels,
  # and S representing the stones you have.  Each character in S is a type of
  # stone you have.  You want to know how many of the stones you have are also
  # jewels.
  
  # The letters in J are guaranteed distinct, and all characters in J and S are
  # letters. Letters are case sensitive, so "a" is considered a different type of
  # stone from "A".
  
  # Example 1:
  
  # Input: J = "aA", S = "aAAbbbb"
  # Output: 3
  # Example 2:
  
  # Input: J = "z", S = "ZZ"
  # Output: 0
  
  # Note:
  # S and J will consist of letters and have length at most 50.
  # The characters in J are distinct.
  
  class Solution:
      def numJewelsInStones(self, J, S):
          """
          :type J: str
          :type S: str
          :rtype: int
          """
          jewels = set(J)
          result = [stone in jewels for stone in S]
  
          return sum(result)
subject: Make code more pythonic