syntax – Nested dictionary comprehension python

syntax – Nested dictionary comprehension python

{inner_k: myfunc(inner_v)} isnt a dictionary comprehension. Its just a dictionary.

Youre probably looking for something like this instead:

data = {outer_k: {inner_k: myfunc(inner_v) for inner_k, inner_v in outer_v.items()} for outer_k, outer_v in outer_dict.items()}

For the sake of readability, dont nest dictionary comprehensions and list comprehensions too much.

Adding some line-breaks and indentation:

data = {
    outer_k: {inner_k: myfunc(inner_v)} 
    for outer_k, outer_v in outer_dict.items()
    for inner_k, inner_v in outer_v.items()
}

… makes it obvious that you actually have a single, 2-dimensional dict comprehension. What you actually want is probably:

data = {
    outer_k: {
        inner_k: myfunc(inner_v)
        for inner_k, inner_v in outer_v.items()
    } 
    for outer_k, outer_v in outer_dict.items()
}

(which is exactly what Blender suggested in his answer, with added whitespace).

syntax – Nested dictionary comprehension python

{ok: {ik: myfunc(iv) for ik, iv in ov.items()} for ok, ov in od.items()}  

where
ok-outer key
ik-inner key
ov-outer value
iv-inner value
od-outer dictionary
This is how i remember.