# Question: Is there a function to flatten a nested dictionary?
**URL:** https://discourse.julialang.org/t/question-is-there-a-function-to-flatten-a-nested-dictionary/54462
**Category:** General Usage
**Tags:** json, dictionary
**Created:** [February 2, 2021, 2:09pm UTC](https://discourse.julialang.org/t/question-is-there-a-function-to-flatten-a-nested-dictionary/54462 "2021-02-02T14:09:11Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@florian](https://discourse.julialang.org/u/florian)
#### Post date: [February 2, 2021, 2:09pm UTC](https://discourse.julialang.org/t/question-is-there-a-function-to-flatten-a-nested-dictionary/54462/1 "2021-02-02T14:09:11Z")
Hi everyone, I’m facing the following problem: Suppose I have a nested dictionary like
```julia
data = Dict(
"id" => 42,
"name" => Dict("first" => "John", "last" => "Doe", "nick" => nothing))
```
which I want to flatten into:
```julia
data_flat = Dict(
"id" => 42,
"name.first" => "John",
"name.last" => "Doe",
"name.nick" => nothing
)
```
My question is the following: Is there function that does this? Something like flatten\_dict(dict, sep=“.”), or would I have to solve this manually by looping through my nested data? I looked trough the JSON.jl package but either there is no such thing or I missed it.
---
### Author:  [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)
#### Post date: [February 2, 2021, 2:52pm UTC](https://discourse.julialang.org/t/question-is-there-a-function-to-flatten-a-nested-dictionary/54462/2 "2021-02-02T14:52:53Z")
I am not sure if there is something that fits your exact need, but it does not seem something so hard to implement.
```julia
function rec_flatten_dict(d, prefix_delim = ".")
new_d = empty(d)
for (key, value) in pairs(d)
if isa(value, Dict)
flattened_value = rec_flatten_dict(value, prefix_delim)
for (ikey, ivalue) in pairs(flattened_value)
new_d["$key.$ikey"] = ivalue
end
else
new_d[key] = value
end
end
return new_d
end
```
Creates some intermediary structs, so it is not a solution with the greatest performance, but it does the job.
```julia
julia> rec_flatten_dict(data)
Dict{String,Any} with 4 entries:
"name.last" => "Doe"
"name.nick" => nothing
"name.first" => "John"
"id" => 42
```
---
### Author:  [@FPGro](https://discourse.julialang.org/u/FPGro)
#### Post date: [February 2, 2021, 2:56pm UTC](https://discourse.julialang.org/t/question-is-there-a-function-to-flatten-a-nested-dictionary/54462/3 "2021-02-02T14:56:21Z")
> [@Henrique\_Becker](#):
>
> ```julia
> if isa(value, Dict)
> rec_flatten_dict(value, prefix_delim)
> for (ikey, ivalue) in pairs(value)
> new_d["$key.$ikey"] = ivalue
> end
> else
>
> ```
Since this doesn’t work in place, you could change the recursion like s:
```julia
if isa(value, Dict)
flattened_value = rec_flatten_dict(value, prefix_delim)
for (ikey, ivalue) in pairs(flattened_value)
new_d["$key.$ikey"] = ivalue
end
else
```
---
### Author:  [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)
#### Post date: [February 2, 2021, 2:58pm UTC](https://discourse.julialang.org/t/question-is-there-a-function-to-flatten-a-nested-dictionary/54462/4 "2021-02-02T14:58:22Z")
Well spotted, I will fix it.
---
### Author:  [@florian](https://discourse.julialang.org/u/florian)
#### Post date: [February 2, 2021, 3:08pm UTC](https://discourse.julialang.org/t/question-is-there-a-function-to-flatten-a-nested-dictionary/54462/5 "2021-02-02T15:08:43Z")
Thank you for your answer, and for even providing working code! I thought before I try to do it manually I should ask if I missed something that’s already available.