# Taking derivative of abstract function pattern in sympy

**URL:** <https://discourse.julialang.org/t/taking-derivative-of-abstract-function-pattern-in-sympy/45870>\
**Category:** New to Julia\
**Created:** [August 31, 2020, 10:21pm UTC](https://discourse.julialang.org/t/taking-derivative-of-abstract-function-pattern-in-sympy/45870 "2020-08-31T22:21:42Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![samerb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/samerb/32/9242_2.png) [@samerb](https://discourse.julialang.org/u/samerb)\
**Post date:** [August 31, 2020, 10:21pm UTC](https://discourse.julialang.org/t/taking-derivative-of-abstract-function-pattern-in-sympy/45870/1 "2020-08-31T22:21:42Z")

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I want to compute a derivative of an expression involving an abstract function like x_g(x) or the mixed partial of x_g(x)/(g(x)+g(y)).

Based on the original python docs [here](https://docs.sympy.org/latest/modules/functions/index.html), I tried:

```julia
using SymPy
x = symbols("x")
h = function("h")
diff(x*h(x))

```

But the line `h=function("h")` is giving me an error:  
`syntax: expected "(" in function definition `

Any suggestions? Thanks

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**Author:** ![j\_verzani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/j_verzani/32/8551_2.png) [@j\_verzani](https://discourse.julialang.org/u/j_verzani)\
**Post date:** [August 31, 2020, 10:31pm UTC](https://discourse.julialang.org/t/taking-derivative-of-abstract-function-pattern-in-sympy/45870/2 "2020-08-31T22:31:00Z")

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> [@samerb](#):
>
> `diff(x*h(x))`

Try: `h = SymFunction("h")`.