使用Python表達式的深度

Question

如何找出python中表達式的深度？我寫的代碼很適合像[[1,2],[1,2,[3,6,54]]輸入，而不是那些象depth (['+', ['expt', 'x', 2], ['expt', 'y', 2]]) => 2和depth(('/', ('expt', 'x', 5), ('expt', ('-', ('expt', 'x', 2), 1), ('/', 5, 2)))) => 4

a=0 
k=0 
j=0 
maxli=[] 
li =[[1,2],[1,2,[3,6,54]] # list whose depth is to be found 
#print len(li) 

def depth(x): 


    global a,k,j 
    j=j+1 
    print" j's value is ",j 
    for i in x: 

     for h in range(len(li)): # runs loop through the items of the list 
      if i== li[h] : k=0 

     if isinstance(i,(tuple,list)) == True: #if we find that there is list 
     k=k+1 

     # print "this is for item",i 
     # print k 
     depth(i) 

    a=k 
    maxli.append(a) # putting the values of a in maxli 

depth(li) 
print "The depth of tree is :",max(maxli) 

Answer 1

利用遞歸這裏是通過函數的返回值，而不是通過操縱全局變量的正確方法。你可以定義一個深度函數如下：

def is_list(x): 
    return hasattr(x,'__getitem__') and type(x) != str 

def depth(l): 
    if not is_list(l): return 0 
    maxdepth = 0 
    for elem in l: 
     maxdepth = max(maxdepth, depth(elem)) 
    return maxdepth + 1 

的