Negative weight cycle Bellman Ford

#User function Template for python3
#T.C=O(ev)
#initially we select a vertex as source and find out the distance to other vertices .
#we relax n-1 iterations. If we found any changes at nth iteration it means there is a negative edge cycle
class Solution:
    def isNegativeWeightCycle(self, n, edges):
        dis=[float('inf')]*n
        dis[0]=0
        for _ in range(n-1):
            update=False
            for i,j,k in edges:
                if dis[j]>dis[i]+k:
                    dis[j]=dis[i]+k
                    update=True
            if update==False:
                return False
        update=False
        for i,j,k in edges:
            if dis[j]>dis[i]+k:
                dis[j]=dis[i]+k
                update=True
        return update==True