Understanding C++ and Python Array Calculations

The opencv image processing program has been rewritten to C++→Python.
Among them, there was an element-by-element subtraction of the array (120, 109, 3), but this result does not fit between the two programs.
The results so far are exactly the same and should only be calculations of (the same number) - (the same number).

I'd appreciate it if you could give me some tips on how to do it or what's wrong.
I look forward to your kind cooperation.

4/15 Add

Regarding the code, please consider src and src2 as images.
What exactly do you want to do?
○ C++

 // src, src2 is cv::Mat type
for(inti=0;i<3,++i){ 
    // Repeat this action three times
    src = src-src2;
}

○ Python

#src,src2 is of type numpy.ndarray
for i in range (3):
    // Repeat this action three times
    src = src-src2

The header relationship is opencv2(C++) and cv2, numpy(Python).
Also, please let me know if you feel that there is a lack of information.