How to store numpy two dimensional array onto disk as a kind of binary format which can be read with C++

Question

I have python two dimensional numpy arrays and I want to change them into binary format which can be read with C++, As you know, two dimensional array in C++ is kind of one dimensional array with two pointers which are used to locate elements. Could you tell me which function in python can be used to do the job or any other solution?

Answer 1

This is too long for a comment, but probably not complete enough to run on it's own. As Tom mentioned in the comments on your question, using a library that saves and loads to a well defined format ( hdf5 , .mat ) in python and C++ is probably the easiest solution. If you don't want to find and setup such a library, read on.

Numy has the ability to save data using numpy.save (see this ), The format (described here ) states there is a header, with information on the datatype and number of array shape, followed by the data. So, unless you want to write a fully featured parser (you don't), you should ensure python consistently saves data as a float64 (or whichever type you want), in c order (fortran ordering is the other option).

Then, the C++ code just needs to check that the array data type is float64 , the correct ordering is used, and how large the array is. Allocate the appropriate amount of memory, and you can load that number of bytes from the file directly into the allocated memory. To create 2d indexing you'll need to allocate an array of pointers to each 'row' in the allocated memory.

Or just use a library that will handle all of that for you.