调用将MATLAB函数句柄作为Matlab的参数的python函数 [英] Call a python function that takes in a MATLAB function handle as argument from matlab

问题描述

我正在尝试使用MATLAB环境中的scipy.optimize.differential_evolution(python).

I'm trying to use the scipy.optimize.differential_evolution (python) from MATLAB environment.

到目前为止，我已经可以调用differential_evolution函数.唯一的问题是它显然无法接受MATLAB函数句柄作为参数.

So far, I am able to call the differential_evolution function. The only problem is that it apprently cannot receive MATLAB function handles as an argument.

我收到以下错误:

使用py.scipy.optimize.differential_evolution处理MATLAB时出错 不支持函数'@(x)x(1).^ 2. * x(2).^ 2'.使用手柄 Python函数.

Error using py.scipy.optimize.differential_evolution Handle to MATLAB function '@(x)x(1).^2.*x(2).^2' is not supported. Use a handle to a Python function.

是否有一些简洁的方法或函数可以将MATLAB函数句柄转换"为python函数，以便我可以使用scipy中的简洁优化函数?

Is there some neat way or function to "convert" a MATLAB function handle into a python function, so that I could use the neat optimization function from scipy?

推荐答案

我不确定，但我怀疑您想做的事无法完成.

I'm not sure but I suspect that what you want can't be done.

首先，如果您将其传递给MATLAB匿名函数，则python接口中的任何内容都会给您该错误:

Firstly, anything in the python interface will give you that error if you pass it a MATLAB anonymous function:

>> py.print(@(x) x)     
Error using py.print
Handle to MATLAB function '@(x)x' is not supported. Use a handle to a Python function.

因此，似乎引擎意味着它，您必须放弃MATLAB函数.我们可以尝试将您的匿名函数转换为python函数，但是我不知道这是怎么可能的.我怀疑这根本不可能，因为最直接，最简单的自定义函数是lambda.但是py.lambda不存在，我们甚至不能通过调用py.eval来愚弄MATLAB引擎:

So it seems the engine means it, and you have to give up MATLAB functions. We could try converting your anonymous function to a python one...but I couldn't figure out how this was possible. I suspect it isn't possible at all, since the most straightforward and simplest custom function would be a lambda. But py.lambda doesn't exist and we can't even fool the MATLAB engine by calling py.eval:

>> py.lambda           
Undefined variable "py" or class "py.lambda".

>> py.eval('lambda x: x')
Python Error: SystemError: frame does not exist

>> py.eval('def foo(x): return x')
Python Error: SystemError: frame does not exist

这非常有力地表明，一旦有了MATLAB匿名函数，就无法将其转换为python函数.

This very strongly suggests that once you have a MATLAB anonymous function you can't turn it into a python one.

直接的问题是:您真的需要MATLAB匿名函数吗?您也可以使用适当的python函数(或lambda)，并将可能的其他参数作为args传递给基础scipy.optimize函数.您可以在python文件中定义自定义函数，然后在MATLAB中import定义自定义函数，并使用相应的函数句柄.这将是您摆脱困境的直接方法.

The straightforward question is: do you really need a MATLAB anonymous function? You could just as well use a proper python function (or lambda) and pass possible other arguments to the underlying scipy.optimize function as args. You could define your custom function in a python file and import that from MATLAB and use the corresponding function handle. This would be the straightforward way out from your situation.

还请注意，尽管缺少MATLAB函数处理支持，但

Also note that while the lack of MATLAB function handle support is not explicitly mentioned among the limitations, the section of the documentation detailing supported data types makes this remark:

MATLAB输入参数类型-仅标量值
函数句柄@py. module.function ，仅适用于Python函数

MATLAB Input Argument Type — Scalar Values Only
function handle @py.module.function, to Python functions only

Python函数的区别与以下事实相符:即使最简单的Python函数也拒绝接受MATLAB函数句柄.

The distinction for Python functions is in line with the fact that even the simplest Python functions refuse to accept MATLAB function handles.

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