# How to pass a SymPy expression supported by JuMP

**URL:** <https://discourse.julialang.org/t/how-to-pass-a-sympy-expression-supported-by-jump/62109>\
**Category:** Optimization (Mathematical)\
**Tags:** jump, sympy\
**Created:** [May 31, 2021, 6:21am UTC](https://discourse.julialang.org/t/how-to-pass-a-sympy-expression-supported-by-jump/62109 "2021-05-31T06:21:14Z")\
**Posts on this page:** 1\
**Showing post:** 3

<div class="post-metadata">

**Author:** ![maoc](https://avatars.discourse-cdn.com/v4/letter/m/58956e/32.png) [@maoc](https://discourse.julialang.org/u/maoc)\
**Post date:** [May 31, 2021, 1:59pm UTC](https://discourse.julialang.org/t/how-to-pass-a-sympy-expression-supported-by-jump/62109/3 "2021-05-31T13:59:27Z")

</div>

Hi, I do this

```julia
x = Sym("x")
y = Sym("y")
expr = x^2 + y
fn = lambdify( expr )

```

and the model

```julia
model = Model(Ipopt.Optimizer)
l = zeros(1,2)
@variable(model, x[j = 1:2] >= 0 )

register(model, :fn,2, fn, autodiff = true)

#obj function
@NLobjective(model,Min,fn)
print(model)
Unexpected object #99 (of type SymPy.var"#99#100"{SymPy.var"###792"} in nonlinear expression.

Stacktrace:
 [1] error(::String) at .\error.jl:33
 [2] _parse_NL_expr_runtime(::Model, ::Function, ::Array{JuMP._Derivatives.NodeData,1}, ::Int64, ::Array{Float64,1}) at C:\Users\xxxxx\.julia\packages\JuMP\e0Uc2\src\parse_nlp.jl:223
 [3] top-level scope at C:\Users\xxxxx\.julia\packages\JuMP\e0Uc2\src\parse_nlp.jl:247
 [4] top-level scope at C:\Users\xxxxx\.julia\packages\JuMP\e0Uc2\src\macros.jl:1368
 [5] top-level scope at In[92]:8
 [6] include_string(::Function, ::Module, ::String, ::String) at .\loading.jl:1091

```

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