# Where to put a bunch of constants?
**URL:** https://discourse.julialang.org/t/where-to-put-a-bunch-of-constants/76885
**Category:** General Usage
**Tags:** question, constants
**Created:** [February 22, 2022, 7:05am UTC](https://discourse.julialang.org/t/where-to-put-a-bunch-of-constants/76885 "2022-02-22T07:05:09Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@marianoarnaiz](https://discourse.julialang.org/u/marianoarnaiz)
#### Post date: [February 22, 2022, 7:05am UTC](https://discourse.julialang.org/t/where-to-put-a-bunch-of-constants/76885/1 "2022-02-22T07:05:09Z")
Hi everyone.
I am developing a set of scripts for geophysics in Julia and at the core of many of my codes I have a bunch of values (maybe they can be consider Julia Constants at some point) but in general they are physical constants (like the Earth’s mean Radius or the Core’s Mass).
Now, many of the users won’t bother changing this, but someone might. Is there a good way to place them in a file for easy modification? What would you recommend?
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### Author:  [@jar1](https://discourse.julialang.org/u/jar1)
#### Post date: [February 22, 2022, 8:07am UTC](https://discourse.julialang.org/t/where-to-put-a-bunch-of-constants/76885/2 "2022-02-22T08:07:20Z")
Some are available in
[https://juliaphysics.github.io/PhysicalConstants.jl/stable/constants/](https://juliaphysics.github.io/PhysicalConstants.jl/stable/constants/)
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### Author:  [@Jeff\_Emanuel](https://discourse.julialang.org/u/Jeff_Emanuel)
#### Post date: [February 22, 2022, 5:42pm UTC](https://discourse.julialang.org/t/where-to-put-a-bunch-of-constants/76885/3 "2022-02-22T17:42:08Z")
> [@marianoarnaiz](#):
>
> set of scripts
Scripts bad, modules good.
> [@marianoarnaiz](#):
>
> but someone might…What would you recommend?
I recommend against such speculative generalization. If you must, because you think the users might try to operate on other celestial bodies, perhaps your functions can accept a Planet parameter, and the module would provide a function to return an earth instance of Planet. The functions may even make the planet parameter default to earth.
---
### Author:  [@lmiq](https://discourse.julialang.org/u/lmiq)
#### Post date: [February 22, 2022, 5:49pm UTC](https://discourse.julialang.org/t/where-to-put-a-bunch-of-constants/76885/4 "2022-02-22T17:49:07Z")
One way to structure it, without relying on global constants:
```julia
julia> module MyPackage
export myfunction, MyConstants
Base.@kwdef struct MyConstants
a::Int=10
b::Float64=1e-3
end
function myfunction(x;constants=MyConstants())
(;a,b) = constants
return a*x^b
end
end
Main.MyPackage
julia> using .MyPackage
julia> myfunction(5.0)
10.016107337527293
julia> myfunction(5.0,constants=MyConstants(b=1e-2))
10.162245912673256
```