python 的 matlab 引擎中的 save() 命令

Question

我正在为 Python 使用 MATLAB 引擎 API https://nl.mathworks.com/help/matlab/matlab-engine-for-python.html

我想打开并保存一个文件。

#import and start the engine
import matlab.engine
eng = matlab.engine.start_matlab()
print('Matlab engine started')
#File of interest
myBadFile='test.mat'
#Synchronize python/matlab working directory
eng.cd(os.getcwd(),nargout=0)
print(eng.pwd())
#Read file contents
VALUES=eng.load(myBadFile,nargout=1)

到目前为止一切顺利。我真的很惊讶它运行得如此顺利。

我在VALUES上做我的东西，然后我想再次保存它。如果我这样做

VALUES=eng.save(myBadFile+'.test','VALUES','-v6',nargout=0)

我得到：

MatlabExecutionError: Variable 'VALUES' not found.

如果我这样做

VALUES=eng.save(myBadFile+'.test',VALUES,'-v6',nargout=0)

我明白了

MatlabExecutionError: Argument must contain a character vector.

那么如何保存我的 VALUES，它在 python 环境中是一个有效变量，但在 matlab 中显然看不到它？

Answer 1

save operates on the variables contained in MATLAB's workspace, and Python does not share scope with the MATLAB engine instance(s). The matlab.engine instance, however, does have a workspace属性，定义如下：

Python dictionary containing references to MATLAB variables. You can assign data to, and get data from, a MATLAB variable through the workspace. The name of each MATLAB variable you create becomes a key in the workspace dictionary. The keys in workspace must be valid MATLAB identifiers (for example, you cannot use numbers as keys).

您可以使用它在 MATLAB 的范围内放置变量。

此代码，例如：

import matlab.engine
eng = matlab.engine.start_matlab()
x = [1, 2, 3]
eng.save('test.mat', 'x')

如上失败：

Error using save
Variable 'x' not found.

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\excaza\AppData\Roaming\Python\Python36\site-packages\matlab\engine\matlabengine.py", line 78, in __call__
    _stderr, feval=True).result()
  File "C:\Users\excaza\AppData\Roaming\Python\Python36\site-packages\matlab\engine\futureresult.py", line 68, in result
    return self.__future.result(timeout)
  File "C:\Users\excaza\AppData\Roaming\Python\Python36\site-packages\matlab\engine\fevalfuture.py", line 82, in result
    self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)
matlab.engine.MatlabExecutionError: Variable 'x' not found.

但是一旦我们将 x 复制到 workspace 字典中就可以正常工作：

import matlab.engine
eng = matlab.engine.start_matlab()
x = [1, 2, 3]
eng.workspace['x'] = x
eng.save('test.mat', 'x')

python 的 matlab 引擎中的 save() 命令

save() command in matlab engine for python

python

workspace

matlab

matlab-engine

mat-file