Minimal NumPy array from C++

• https://github.com/simoncblyth/np/

I searched and they were all excessively complicated for my taste, so I rolled my own:

• https://github.com/search?q=NPY+C%2B%2B

Documentation of the NPY serialization format

• https://github.com/numpy/numpy/blob/master/doc/neps/nep-0001-npy-format.rst

NP.hh(+NPU.hh) provides a lightweight header only NPY writing/reading. Just copy into your project and #include "NP.hh" to use.

Tests of the header

cd tests
./go.sh

Or do some manual testing:

clang NPTest.cc -std=c++11 -lc++ -o /tmp/NPTest
gcc NPTest.cc -std=c++11 -lstdc++ -o /tmp/NPTest
   ## build test executable using your compiler,
   ## implementation is entirely in headers NP.hh and NPU.hh

/tmp/NPTest /tmp/a.npy
   ## run test executable writing a test NumPy array to the path given

python -c "import numpy as np ; np.save('/tmp/b.npy', np.linspace(0,39,40,dtype=np.float32).reshape(-1,4) ) "
   ## do the same thing from python using NumPy

ls -l /tmp/a.npy /tmp/b.npy
   ## check the byte sizes are the same

diff /tmp/a.npy /tmp/b.npy
    ## check for a match

xxd /tmp/a.npy
xxd /tmp/b.npy
    ## hexdump if there are differences

python -c "import numpy as np ; print np.load('/tmp/a.npy') "
   ## load and print the C++ written NumPy array

python -c "import numpy as np ; print np.load('/tmp/b.npy') "
   ## load and print the python written NumPy array

A few references

• https://github.com/diana-hep/c2numpy
• https://jcastellssala.com/2014/02/01/npy-in-c/
• https://github.com/onai/npio