# Looking for a key in a nested dict
**URL:** https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211
**Category:** New to Julia
**Created:** [November 6, 2018, 11:21am UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211 "2018-11-06T11:21:00Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@Olivier\_Merchiers](https://discourse.julialang.org/u/Olivier_Merchiers)
#### Post date: [November 6, 2018, 11:21am UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/1 "2018-11-06T11:21:00Z")
Hello everyone,
I’m trying to search for a specific key in a deeply nested dict which can also contain arrays.
In a first step I import a yaml file which I parse using YAML.jl. This gives me a nested dict.
If we take the truncated example of the README file from the YAML.jl package:
```julia
# data.yml
receipt: Oz-Ware Purchase Invoice
date: 2012-08-06
customer:
given: Dorothy
family: Gale
```
This would be parsed as
```julia
julia> using YAML
julia> data = YAML.load(open("data.yml"))
Dict{Any,Any} with 3 entries:
"receipt" => "Oz-Ware Purchase Invoice"
"customer" => Dict{Any,Any}(Pair{Any,Any}("given", "Dorothy"),Pair{Any,Any}("…
"date" => 2012-08-06
```
How would I access in for instance the value of the “given” form the dict corresponding to “customer”?
I would like to achieve this in a general way, where there could be multiple levels of nesting.
I tried to translate the following python code which I found on [StackExchange](https://codereview.stackexchange.com/questions/201754/getting-a-keys-value-in-a-nested-dictionary):
```julia
def retrieve_nested_value(mapping, key_of_interest):
mappings = [mapping]
while mappings:
mapping = mappings.pop()
try:
items = mapping.items()
except AttributeError:
# we didn't store a mapping earlier on so just skip that value
continue
for key, value in items:
if key == key_of_interest:
yield value
else:
# type of the value will be checked in the next loop
mappings.append(value)
```
where `mapping` is a dict.
This is my attempt to translate it to julia
```julia
function retreive_nested_value(dict, key_of_interest)
dictv = [dict]
while isempty(dictv) == false
dict = pop!(dictv)
for (key,value) in dict
if key == key_of_interest
return value
else
dictv = [dictv , [value]]
end
end
end
end
```
But unfortunately, it gives me only the values of the first level (same as get(dict, key\_of\_interest,0)). I cannot fetch the values of the lower levels.
How would one do this in julia?
Many thanks in advance,
Olivier
---
### Author:  [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)
#### Post date: [November 6, 2018, 1:16pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/2 "2018-11-06T13:16:51Z")
Wouldn’t this be a classic case of recursion? This code can be easily modified to push multiple positive results to an array.
```julia
function retrieve(dict, key_of_interest)
for (key, value) in dict
if key == key_of_interest
return value
end
if value isa Dict
return retrieve(value, key_of_interest)
end
end
end
```
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [November 6, 2018, 1:21pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/3 "2018-11-06T13:21:59Z")
Nice, could possibly also descend into any `AbstractDict`.
---
### Author:  [@Olivier\_Merchiers](https://discourse.julialang.org/u/Olivier_Merchiers)
#### Post date: [November 6, 2018, 1:27pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/4 "2018-11-06T13:27:59Z")
Thanks a lot for looking into this,
Unfortunately, the code does not return anything.
Should I do something extra to get the values?
I tried on both julia 0.6.4 and 0.7
Could you do it without recursion?
Thanks again
---
### Author:  [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)
#### Post date: [November 6, 2018, 1:31pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/5 "2018-11-06T13:31:16Z")
It definitely returns something, provided the key is the Dict somewhere. Could you give a minimum working example? Recursion is definitely the default way to solve these kinds of problems.
---
### Author:  [@Olivier\_Merchiers](https://discourse.julialang.org/u/Olivier_Merchiers)
#### Post date: [November 6, 2018, 2:11pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/7 "2018-11-06T14:11:34Z")
> t definitely returns something, provided the key is the Dict somewhere.
Yes indeed. My bad. It works fine when the key occurs only once.
If it occurs multiple times, then nothing is returned.
I’m trying now to add multiple occurrences into an array as you said.
Thanks again!
---
### Author:  [@Olivier\_Merchiers](https://discourse.julialang.org/u/Olivier_Merchiers)
#### Post date: [November 6, 2018, 2:12pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/8 "2018-11-06T14:12:32Z")
I’m not sure I understand what you mean.
Could you expand a little?
---
### Author:  [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)
#### Post date: [November 6, 2018, 2:16pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/9 "2018-11-06T14:16:50Z")
If it ocurs multiple times, only the first appearance of the key is returned. Here is an implementation that takes into account multiple returns
```julia
function retrieve(dict, key_of_interest, output = []) # default value is an empty array
for (key, value) in dict
if key == key_of_interest
push!(output, value)
end
if value isa AbstractDict
retrieve(value, key_of_interest, output)
end
end
return output
end
```
---
### Author:  [@Olivier\_Merchiers](https://discourse.julialang.org/u/Olivier_Merchiers)
#### Post date: [November 6, 2018, 2:27pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/10 "2018-11-06T14:27:59Z")
ok, great!
I just managed a similar solution, but yours is much more elegant.
Here is mine:
```julia
function retrieve2(dict, key_of_interest)
values = Vector{Any}()
for (key, value) in dict
if key == key_of_interest
append!(values,[value])
end
if value isa Dict
val = retrieve(value, key_of_interest)
append!(values,val)
end
end
return values
end
```
Thanks again to all of you!
---
### Author:  [@system](https://discourse.julialang.org/u/system)
#### Post date: [November 18, 2018, 2:28pm UTC](https://discourse.julialang.org/t/looking-for-a-key-in-a-nested-dict/17211/11 "2018-11-18T14:28:01Z")
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