ID3 algorithm: RecursionError: maximum recursion depth exceeded in comparison

Question

I have this function to build ID3 decision tree:

  def buildTree(df,tree=None): 
        Class = df.keys()[-1]   #To make the code generic, changing target variable class name
        
        #Here we build our decision tree
    
        #Get attribute with maximum information gain
        node = find_winner(df)
        
        #Get distinct value of that attribute e.g Salary is node and Low,Med and High are values
        attValue = np.unique(df[node])
        #Create an empty dictionary to create tree    
        if tree is None:                    
            tree={}
            tree[node] = {}
        
       #We make loop to construct a tree by calling this function recursively. 
        #In this we check if the subset is pure and stops if it is pure. 
        for value in attValue:
            
            subtable = get_subtable(df,node,value)
            clValue,counts = np.unique(subtable['For the management of this project'],return_counts=True)
            if len(counts)==1:#Checking purity of subset
                tree[node][value] = clValue[0]                                                    
            else:        
                tree[node][value] = buildTree(subtable) #Calling the function recursively 
                       
        return tree

I got this error:

RecursionError: maximum recursion depth exceeded in comparison

I tried to fix it using sys.setrecursionlimit(), but I still have the same error. I thought I should minimize the depth of my decision tree.