leetcode 169. Majority Element python

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

class Solution(object):
    def majorityElement(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        a = len(nums)
        b = a /2
        for x in nums:
            if nums.count(x) > b:
                return x

Submission Result: Time Limit Exceeded              

   return sorted(nums)[len(nums)/2]