byteswap() looks like a general endian solution for ndarrays:

https://stackoverflow.com/questions/49578507/fast-way-to-reverse-float32-endianness-in-binary-file

numpy.memmap(infile, dtype=numpy.int32).byteswap().tofile(outfile)

numpy.memmap(infile, dtype=numpy.int32).byteswap(inplace=True).flush()

Bill

On 2023-01-01 08:31, Jerome Kieffer wrote:

On Sun, 01 Jan 2023 05:31:55 -0800
Bill Ross <bross_phobrain@sonic.net> wrote:

Thanks!

Java is known to be big-endian ... your CPU is probably little-endian.   

$ lscpu | grep -i endian
Byte Order: Little Endian

Numpy has the tools to represent an array of double BE.   

Is there a lower-level ndarray method that writes an array that could be
used this way?

One example:

numpy.array([1,2,3], dtype=">d").tobytes()
b'?\xf0\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00\x00@\x08\x00\x00\x00\x00\x00\x00'

numpy.array([1,2,3], dtype="<d").tobytes()
b'\x00\x00\x00\x00\x00\x00\xf0?\x00\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00\x08@'

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