# How to call a Matlab function in Python from matlab.engine using the user's input (variable of type string) as the name of the function?

## Question:

I have a Matlab function name as a string (the variable name is ‘function_name’), which is an input from a user, and I need to somehow call that function from Python. Below you can see how I was trying to call this function using the variable name, but it exited with the following error: `(<class 'matlab.engine.MatlabExecutionError'>, MatlabExecutionError("Undefined function 'chsn_agthm' for input arguments of type 'uint8'.n"), <traceback object at 0x0000015D14323C00>)`

```
import matlab.engine
eng = matlab.engine.start_matlab()
res = eng.function_name(input1, input2, nargout=2)
```

## Answers:

The problem is that `function_name`

needs to be a statement in the python code, but is given as string. To resolve this, my suggestion would be not to call `function_name`

directly, but to always call MATLAB’s `feval`

function with `function_name`

as first input argument, i.e.

```
res = eng.feval( function_name, input1, input2, nargout=2)
```

`feval`

is then called by the MATLAB engine and invokes the function with the name `function_name`

using the other arguments (apart from `nargout=2`

) as input.

For further information on `feval`

please have a look at https://de.mathworks.com/help/matlab/ref/feval.html.

*Alternative approach:*

It might also be possible to construct a string that contains a valid python expression including `function_name`

and then to call this expression using pythons `eval()`

.