# How to generate variables and assign values from a dictionary by metapgramming?
**URL:** https://discourse.julialang.org/t/how-to-generate-variables-and-assign-values-from-a-dictionary-by-metapgramming/37638
**Category:** General Usage
**Tags:** metaprogramming
**Created:** [April 15, 2020, 1:33pm UTC](https://discourse.julialang.org/t/how-to-generate-variables-and-assign-values-from-a-dictionary-by-metapgramming/37638 "2020-04-15T13:33:55Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Xing\_Shi\_Cai](https://discourse.julialang.org/u/Xing_Shi_Cai)
#### Post date: [April 15, 2020, 1:33pm UTC](https://discourse.julialang.org/t/how-to-generate-variables-and-assign-values-from-a-dictionary-by-metapgramming/37638/1 "2020-04-15T13:33:55Z")
I am using `ArgParse.jl` to parse command line arguments. It returns a dictionary. But I would prefer to generate variables so it’s easier to use them. I tried to use Meta programming as follows
```julia
function main()
parsed_args = parse_commandline()
# Turn the dictionary into variables
for key in keys(parsed_args)
ex = Meta.parse("const $key = parsed_args[\"$key\"]")
eval(ex)
end
do_something(n1, n2, d1, d2)
end
```
But I got
```julia
ERROR: LoadError: UndefVarError: parsed_args not defined
```
What did I do wrong?
---
### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [April 15, 2020, 1:43pm UTC](https://discourse.julialang.org/t/how-to-generate-variables-and-assign-values-from-a-dictionary-by-metapgramming/37638/2 "2020-04-15T13:43:36Z")
> [@Xing\_Shi\_Cai](#):
>
> What did I do wrong?
`eval` evaluates in global scope. `parsed_args` is in local scope.
---
### Author:  [@Xing\_Shi\_Cai](https://discourse.julialang.org/u/Xing_Shi_Cai)
#### Post date: [April 15, 2020, 1:45pm UTC](https://discourse.julialang.org/t/how-to-generate-variables-and-assign-values-from-a-dictionary-by-metapgramming/37638/3 "2020-04-15T13:45:36Z")
@kristoffer.carlsson Anyway to fix this?
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [April 15, 2020, 1:54pm UTC](https://discourse.julialang.org/t/how-to-generate-variables-and-assign-values-from-a-dictionary-by-metapgramming/37638/4 "2020-04-15T13:54:59Z")
> [@Xing\_Shi\_Cai](#):
>
> ex = Meta.parse(“const $key = parsed\_args["$key"]”) eval(ex)
You probably want `eval(:(const $(Symbol(key)) = $(parsed_args[key])))`. (Note that I’m inserting the _value_ of `parsed_args[key]` directly into the expression tree.) In general, it is _vastly_ more flexible and reliable to build expression trees directly rather than parsing strings.
---
### Author:  [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)
#### Post date: [April 15, 2020, 2:10pm UTC](https://discourse.julialang.org/t/how-to-generate-variables-and-assign-values-from-a-dictionary-by-metapgramming/37638/5 "2020-04-15T14:10:31Z")
> [@Xing\_Shi\_Cai](#):
>
> Anyway to fix this?
Yes, interpolate the values into the expression.