# How to add values in a dictionary of lists?
**URL:** https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192
**Category:** General Usage
**Tags:** question
**Created:** [January 7, 2022, 1:30pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192 "2022-01-07T13:30:57Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@jcbritobr](https://discourse.julialang.org/u/jcbritobr)
#### Post date: [January 7, 2022, 1:30pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/1 "2022-01-07T13:30:57Z")
Hello, good morning.
How to add values in a dictionary that has type (int, vector(int))? Cant understand the error about conversion
```julia
ERROR: LoadError: MethodError: Cannot `convert` an object of type Int64 to an object of type Vector{Tuple{Int64}}
```
```julia
using StatsBase
using Plots
using Combinatorics
using DataStructures
Ω = Dict((i, j) => i+j for i in 1:6 for j in 1:6);
println(length(Ω))
println(Ω)
buffer = DefaultDict{Int64, Vector{Tuple{Int64}}}(0);
for ((i,j), value) in Ω
println("Key: i: $i, j: $j -> $value")
push!(buffer[value], (i, j));
end
```
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [January 7, 2022, 1:49pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/2 "2022-01-07T13:49:10Z")
You have probably mixed up your types you really want a bit, but for your
```julia
buffer = DefaultDict{Int64, Vector{Tuple{Int64}}}(0);
```
the proper push! would be e.g.:
```julia
julia> value=1
1
julia> i=2
2
julia> buffer = DefaultDict{Int64, Vector{Tuple{Int64}}}(0);
julia> push!( buffer, value => [(i,)] )
DefaultDict{Int64, Vector{Tuple{Int64}}, Int64} with 1 entry:
1 => [(2,)]
```
But my guess is, you want something else.
I can just speculate but I think it helps, if you look what a Tuple{Int} really is:
```julia
julia> x=(1,)
(1,)
julia> typeof(x)
Tuple{Int64}
julia> y=(1,2)
(1, 2)
julia> typeof(y)
Tuple{Int64, Int64}
```
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [January 7, 2022, 1:55pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/3 "2022-01-07T13:55:17Z")
But perhaps you want to push into a Vector in the Dict, for this you first have to create the Vector, because
```julia
buffer[value]
```
isn’t defined in your case.
First check if
```julia
buffer[value]
```
exists:
```julia
haskey(buffer,value)
```
and if not create the Vector first:
```julia
v=[(i,)]
push!( buffer, value => v )
```
And if it exists, the push! would be e.g.:
```julia
push!( buffer[value], (4,) )
```
---
### Author:  [@jcbritobr](https://discourse.julialang.org/u/jcbritobr)
#### Post date: [January 7, 2022, 3:00pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/4 "2022-01-07T15:00:05Z")
Thats a bit confusing…
for this
```julia
for ((i,j), value) in Ω
println("Key: i: $i, j: $j -> $value")
push!(buffer, value => [(i, j)]);
end
```
got this error
```julia
ERROR: LoadError: MethodError: Cannot `convert` an object of type
Tuple{Int64{},Int64} to an object of type
Tuple{Int64{}}
```
---
### Author:  [@jcbritobr](https://discourse.julialang.org/u/jcbritobr)
#### Post date: [January 7, 2022, 3:03pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/5 "2022-01-07T15:03:12Z")
What I want is create a key and append in vector of this key, because this will work as a histogram, and I will search for all the values of the vector using only the key
dict[7] will give-me all tuples (i,J) that i+j sums 7
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [January 7, 2022, 3:08pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/6 "2022-01-07T15:08:02Z")
> [@jcbritobr](#):
>
> `push!(buffer, value => [(i, j)]);`
For this you need:
```julia-auto
buffer = DefaultDict{Int64, Vector{Tuple{Int64,Int64}}}(0);
```
---
### Author:  [@jcbritobr](https://discourse.julialang.org/u/jcbritobr)
#### Post date: [January 7, 2022, 3:08pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/7 "2022-01-07T15:08:43Z")
Now, it worked as you said.
```julia
DefaultDict(5 => [(2, 3)], 12 => [(6, 6)], 8 => [(5, 3)], 6 => [(2, 4)], 11 => [(6, 5)], 9 => [(5, 4)], 3 => [(2, 1)], 7 => [(6, 1)], 4 => [(2, 2)], 2 => [(1, 1)], 10 => [(5, 5)])
```
The issue was in the type declaration:
```julia
buffer = DefaultDict{Int64, Vector{Tuple{Int64}}}(0);
```
changing it to
```julia
buffer = DefaultDict{Int64, Vector{Tuple{Int64, Int64}}}(0);
```
worked
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [January 7, 2022, 3:10pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/8 "2022-01-07T15:10:19Z")
But your code has still an issue.
You will never have more than one tuple in any array, because you overwrite if a key already exist in your Dict. You have to check if a key already exist.
---
### Author:  [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)
#### Post date: [January 7, 2022, 3:40pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/9 "2022-01-07T15:40:33Z")
Isn’t the point of using a `DefaultDict` that you don’t have to check if a key already exists?
I imagine this is how the original code was supposed to look, i.e. getting both the value type and the default constructor right.
```julia
using DataStructures
Ω = Dict((i, j) => i+j for i in 1:6 for j in 1:6);
println(length(Ω))
println(Ω)
buffer = DefaultDict{Int, Vector{Tuple{Int, Int}}}(Vector{Tuple{Int, Int}});
for ((i,j), value) in Ω
println("Key: i: $i, j: $j -> $value")
push!(buffer[value], (i, j));
end
```
---
### Author:  [@jcbritobr](https://discourse.julialang.org/u/jcbritobr)
#### Post date: [January 7, 2022, 3:46pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/10 "2022-01-07T15:46:55Z")
yep, this leads to better code, and the issue root cause was the type declaration.
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [January 7, 2022, 3:53pm UTC](https://discourse.julialang.org/t/how-to-add-values-in-a-dictionary-of-lists/74192/11 "2022-01-07T15:53:22Z")
Didn’t know this and I didn’t look into the docs 😉