請解釋這段代碼的工作？

Question

def gSubsets(L): 
    if len(L) == 0: 
     print '2' 
     return [[]] 
    smaller = gSubsets(L[:-1]) 
    extra = L[-1:] 
    print L  
    new = [] 
    for small in smaller: 
     new.append(small+extra) 
    return smaller+new 
print gSubsets([1,2]) 

我是一名Python初學者。我沒有得到如何實際的return在最後並沒有結束，通過獲取：

smaller + new =[[][5]] 

Answer 1

把它分解成塊

def gSubsets(L): #recursive function 
    if len(L) == 0: #when weve reached the last subset we then have to handle an empty list 
     print '2' 
     return [[]] #returns a list of lists for the small in smaller 
    smaller = gSubsets(L[:-1]) #get subsets by recursive call for all elements in the list except the last one 
    extra = L[-1:] #get the last element in the list not used in this recursive call 
    print L  
    new = [] 
    for small in smaller: #loop through list of lists from recursive call 
     new.append(small+extra) #append all combinations of the last element in the list to every other element in the same list to new 
    return smaller+new #return subset with new combinations 

print gSubsets([1,2]) 

通過這種方式輸出

>>> 2 
>>> [1] 
>>> [1, 2] 
>>> [[], [1], [2], [1, 2]] 

，在python中，你應該在你的變量和函數名稱（它的首選語法）中使用下劃線，我也會在你的變量名稱上工作..你希望它們非常具體，所以任何其他人都可以rstand它是什麼馬上。這是我將如何重命名變量。

def generate_subsets_from_list(input_list): 
    if len(input_list) == 0: 
     # print '2' -- not sure why you are printing 2 here? 
     return [[]] 
    subsets = generate_subsets_from_list(input_list[:-1]) 
    last_element = L[-1:] 
    print L  
    return_list = [] 
    for subset in subsets: 
     return_list.append(subset+last_element) 
    return subsets+return_list 

initial_list = [1,2] 
print generate_subsets_from_list(initial_list)