如何迭代地创建嵌套字典？

Question

I want to create a dictionary from a given list, nesting elements as shown below. For instance, given:

lst = range(1, 11)

how do I create a function to create a nested dictionary from this list:

dic = {1: {2: {3: {4: {5: {6: {7: {8: {9: 10}}}}}}}}}

Answer 1

Reverse your list (or better range object). Take the last (now first) element as start value and create a new dict in each iteration through the rest of the reversed list:

>>> r = reversed(range(1, 11))
... d = next(r)
... for x in r:
...     d = {x: d}
... d
...
{1: {2: {3: {4: {5: {6: {7: {8: {9: 10}}}}}}}}}

Answer 2

You could use functools.reduce .

import functools

lst = range(1, 11)
functools.reduce(lambda x, y: {y: x}, reversed(lst))
# {1: {2: {3: {4: {5: {6: {7: {8: {9: 10}}}}}}}}}

Answer 3

You can build it from inside out:

result = {9: 10}

for i in range(8, 0, -1):
    temp = {i: result}
    result = temp    

print(result)
# outputs {1: {2: {3: {4: {5: {6: {7: {8: {9: 10}}}}}}}}}

Answer 4

Start from the innermost value, working outward. At each step, use the previous step's dict as the new val .

def nest_dict(lst):
    my_dict = lst[-1]
    for val in lst[-2::-1]:
        my_dict = {val: my_dict}
    return my_dict

print nest_dict(range(1, 11))

Output:

{1: {2: {3: {4: {5: {6: {7: {8: {9: 10}}}}}}}}}