# Dictionary with multiple identical keys
**URL:** https://discourse.julialang.org/t/dictionary-with-multiple-identical-keys/4269
**Category:** New to Julia
**Created:** [June 14, 2017, 12:32pm UTC](https://discourse.julialang.org/t/dictionary-with-multiple-identical-keys/4269 "2017-06-14T12:32:36Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Daniel\_Scheinerman](https://discourse.julialang.org/u/Daniel_Scheinerman)
#### Post date: [June 14, 2017, 12:32pm UTC](https://discourse.julialang.org/t/dictionary-with-multiple-identical-keys/4269/1 "2017-06-14T12:32:36Z")
I accidentally created a dictionary with multiple identical keys recently. The following code encapsulates what I encountered.
function break\_dict(n)
D = Dict()
r = zeros(Int16,n)
for i=1:n
r[i] += 1
D[r] = sum(r)
end
D, r
end
If you call:
D, r = break\_dict(5)
it returns a dictionary with all keys equal to [1,1,1,1,1] and values 1,2,3,4,5. If you replace “D[r] = sum(r)” with “D[copy(r)] = sum(r)” then you do get five distinct keys as I had initially expected. I am used to Python where keys are immutable so this kind of behavior doesn’t happen. I undertand that “r” is the key not its value. Still having a dictionary with equal keys seems like undesirable behavior. For example, if you ask
length(D)
it returns 5
However,
length(Set(collect(keys(D))))
returns 1. Also,
D[r]
returns 5
D[[1,1,1,1,0] ]
gives an error since that is not a key (though that value was a key at one point in the loop), but
r[end] = 0
D[r]
returns 4.
Thanks for insights!
---
### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [June 14, 2017, 12:41pm UTC](https://discourse.julialang.org/t/dictionary-with-multiple-identical-keys/4269/2 "2017-06-14T12:41:42Z")
We allow mutable keys for flexibility but you must not mutate them in a way that can change their hash and isequal.