Find_No_duplicate_number.py

class Solution(object):
  def singleNumber(self, nums):
    occurrence = {}

    for n in nums:
      occurrence[n] = occurrence.get(n, 0) + 1

    for key, value in occurrence.items():
      if value == 1:
        return key


### Seconf form

  def singleNumber2(self, nums):
    unique = 0
    for n in nums:
      unique ^= n
    return unique

print(Solution().singleNumber2([4, 3, 2, 4, 1, 3, 2]))
# 1