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
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, ...)
libnpy is a header only library. You only need to download npy.hpp into your include path. Neither special compiler flags nor a specific build system are required.
Optional: If you use meson, you can use the provided meson.build file to declare the dependency on libnpy.
The API has changed in the last release. The old C-style API is still available, but might get removed in the future.
#include "npy.hpp"
#include <vector>
#include <string>
int main() {
const std::string path {"data.npy"};
npy::npy_data d = npy::read_npy<double>(path);
std::vector<double> data = d.data;
std::vector<unsigned long> shape = d.shape;
bool fortran_order = d.fortran_order;
}
#include "npy.hpp"
#include <vector>
#include <string>
int main() {
const std::vector<double> data{1, 2, 3, 4, 5, 6};
npy::npy_data d;
d.data = data;
d.shape = {2, 3};
d.fortran_order = false; // optional
const std::string path{"out.npy"};
npy::write_npy(path, d);
}
This will involve an additional copy of the data, which might be undesireable for larger data. The copy can be avoided by using npy::npy_data_ptr as follows.
#include "npy.hpp"
#include <vector>
#include <string>
int main() {
const std::vector<double> data{1, 2, 3, 4, 5, 6};
npy::npy_data_ptr<double> d;
d.data_ptr = data.data();
d.shape = {2, 3};
d.fortran_order = false; // optional
const std::string path{"out.npy"};
npy::write_npy(path, d);
}
See test/ for further examples.
C++14 is required.
The tests can be build with meson>=0.55 and depend on catch2.
cd tests
meson setup builddir
meson test -Cbuilddir
-
Only a few data types are supported.
-
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.
The code is formatted with clang-format. Please test your changes by running the tests and static analysis. Meson automatically builds a target for clang-tidy:
cd tests
meson setup builddir
ninja -C builddir clang-tidy
The project is licensed under the MIT license
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent