C++ library for reading and writing of numpy's .npy files
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libnpy is a simple C++ library for reading and writing of numpy's .npy files.

Refer to format.py for a detailed description of the .npy format.

This libraries primary purpose is writing numerical data easily and efficiently into the .npy format. It also allows reading .npy files, although only a very limited subset of data types are supported.


  • Writing C++ vectors (std::vector) to .npy files
  • Reading (some) simple .npy files into C++ vectors

Supported data types and mapping

Only scalar numeric data types are supported. There is no natural way to represent more complex objects and parsing the header becomes tremendously more complex. Supported types:

  • unsigned integer
  • signed integer
  • floating point
  • complex floating point (std::complex, ...)


''' #include "libnpy.hpp"

// TODO: include example code here

''' See test/ for examples. C++11 is required. If you use g++, use -std=c++11.

Known limitations

  1. Only a few data types are supported.

  2. The numpy header is a literal Python dictionary and the Python syntax is very permissive. libnpy's parser was only tested with numpy's implemenation of the .npy format.


Feel free to send me a pull request, open an issue, or contact me directly.