why my code get that TypeError: list indices must be integers or slices, not str in Python

Question

kmeans_99 = KMeans(n_clusters = 3).fit(X_99)
print(kmeans_99)
labels_99 = kmeans_99.labels_
#Counting the number of the labels in each cluster and saving the data into clustering_classes
clustering_classes_99 = {
 0: [0,0,0],
 1: [0,0,0],
 2: [0,0,0]
}



for i in range(len(y)):
  clustering_classes_99[labels_99[i]][y[i]]     #why this line get error

#Finding the most appeared label in each cluster and computing the purity score

purity_score_99 = (max(clustering_classes_99[0])+max(clustering_classes_99[1])+max(clustering_classes_99[2]))/len(y)
print(f"The purity score is {round(purity_score_99*100,2)} %")

I get TypeError: list indices must be integers or slices, not str. I can't find the solution. I try lot of ways.

This is the error I got:

TypeError                                 Traceback (most recent call last)
<ipython-input-31-95be616a06bd> in <module>()
     12 
     13 for i in range(len(y)):
---> 14   clustering_classes_99[labels_99[i]][y[i]]
     15 
     16 #Finding the most appeared label in each cluster and computing the purity score

TypeError: list indices must be integers or slices, not str

please help me to solve this