Python3 nested dictionary leaking values to other keys

Question

Value assignment leaking over keys when using a dictionary of dictionaries.

Used the fromkeys() function to create the outer dictionary.

Environment: Python 3.6.3

sample_dict = dict.fromkeys(
    [1,0], 
    {}
)
sample_dict[1]['a'] = 1
print(sample_dict)

Output:

{1: {'a': 1}, 0: {'a': 1}}

As you can see, the value gets duplicated for key 0 even when I am only assigning it to key 1.

---

I tried this and it worked as expected:

sample_dict = dict.fromkeys(
    [1,0]
)
sample_dict[1] = {}
sample_dict[1]['a'] = 1
print(sample_dict)

Output:

{1: {'a': 1}, 0: {}}

Is it wrong to nest dictionaries when using the fromkeys() function?