# Assigning value to time dependent symbolic function inside a function

**URL:** <https://discourse.julialang.org/t/assigning-value-to-time-dependent-symbolic-function-inside-a-function/114361>\
**Category:** General Usage\
**Tags:** question, modelingtoolkit\
**Created:** [May 16, 2024, 2:04pm UTC](https://discourse.julialang.org/t/assigning-value-to-time-dependent-symbolic-function-inside-a-function/114361 "2024-05-16T14:04:49Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![PrimulaBunce](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/primulabunce/32/46933_2.png) [@PrimulaBunce](https://discourse.julialang.org/u/PrimulaBunce)\
**Post date:** [May 16, 2024, 2:04pm UTC](https://discourse.julialang.org/t/assigning-value-to-time-dependent-symbolic-function-inside-a-function/114361/1 "2024-05-16T14:04:49Z")

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Hi,

In the following code:

```Julia
using ModelingToolkit

@variables t 

@register_symbolic u(t)

u(t) = 60

```

is there a way I can assign a value to u(t) from inside a function? The following doesn’t work.

```Julia
function assignValue(x)
	u(t) = x
end

assignValue(60)

```

---

<div class="post-metadata">

**Author:** ![baggepinnen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/baggepinnen/32/693_2.png) [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)\
**Post date:** [May 16, 2024, 2:19pm UTC](https://discourse.julialang.org/t/assigning-value-to-time-dependent-symbolic-function-inside-a-function/114361/2 "2024-05-16T14:19:37Z")

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What are you trying to accomplish? Given the information you have provided, you might as well do

```julia
@variables u(t)

equations = [
    u ~ 60
]

```

---

<div class="post-metadata">

**Author:** ![PrimulaBunce](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/primulabunce/32/46933_2.png) [@PrimulaBunce](https://discourse.julialang.org/u/PrimulaBunce)\
**Post date:** [May 16, 2024, 2:28pm UTC](https://discourse.julialang.org/t/assigning-value-to-time-dependent-symbolic-function-inside-a-function/114361/3 "2024-05-16T14:28:35Z")

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Hi, thanks for the response.

I want to simulate a modelingtoolkit model from python. Something like this:

```Python
# Importing the model
from julia import Main
Main.include("model.jl")

# Control input
u = 60

# Simulate
sol = Main.solveModel(u)

```

So, I want to be able to change the control input value from python.

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<div class="post-metadata">

**Author:** ![baggepinnen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/baggepinnen/32/693_2.png) [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)\
**Post date:** [May 16, 2024, 3:18pm UTC](https://discourse.julialang.org/t/assigning-value-to-time-dependent-symbolic-function-inside-a-function/114361/4 "2024-05-16T15:18:56Z")

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If the input is always a constant, you can encode it as a parameter using `@parameters` and then change the value by providing a new value in the parameter map when creating the ODEProblem.

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<div class="post-metadata">

**Author:** ![PrimulaBunce](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/primulabunce/32/46933_2.png) [@PrimulaBunce](https://discourse.julialang.org/u/PrimulaBunce)\
**Post date:** [May 16, 2024, 3:41pm UTC](https://discourse.julialang.org/t/assigning-value-to-time-dependent-symbolic-function-inside-a-function/114361/5 "2024-05-16T15:41:46Z")

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That worked! Thanks a lot 😊