leetcode First Missing Positive python

class Solution(object):
    def firstMissingPositive(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        intlen=len(nums)
        i=0
        while i < intlen:
            if nums[i] > 0 and nums[i] < intlen and nums[i] != nums[nums[i]-1]:
　　　　　　　　　 #get the current num, and put it into it‘s right place
                #for example : if get the third item is 5 ( index is 2, start with 0 ) , so the index of 5 should be 4 
                tmp=nums[nums[i]-1]
                nums[nums[i]-1]=nums[i]
                nums[i]=tmp
            else:
                i+=1
                
        for i in range(intlen):
            if nums[i] != i+1:
                return i+1
                
        return intlen+1