python

Question

我想更改列表的表示形式.. 在这段代码之后我扭曲了输出，我试过没有成功 所以，如果有人能帮助我，我会很感激

empty_rlist = None

def make_rlist(first,rest):
    return (first, rest)

def first(s):
    return s[0]

def rest(s):
    return s[1]

def len_rlist(s):

    length = 0
    while s != empty_rlist:
        s, length = rest(s), length + 1
    return length

def getitem_rlist(s, i):
    while i > 0:
        s, i = rest(s), i - 1
    return first(s)

def make_mutable_rlist():

    contents = empty_rlist

    def length():
        return len_rlist(contents)

    def get_item(ind):
        return getitem_rlist(contents, ind)

    def push_first(value):
        nonlocal contents
        contents = make_rlist(value, contents)

    def pop_first():
        nonlocal contents
        f = first(contents)
        contents = rest(contents)
        return f

    def str():
        return str(contents)

    return {'length':length, 'get_item':get_item, 'push_first':push_first,'pop_first': pop_first, 'str':str }    


my_list = make_mutable_rlist()
for x in range(4):
    my_list['push_first'](x)

print(my_list['str']())     

我需要改变str函数的实现： 这给了我结果

(1, (2, (3, (4, None))))

但我想要的是

[1,2,3,4]