pybind/pybind11

Not clear how to expose existing C++ vector as numpy array

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#1,042 opened on Aug 30, 2017

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 (37 comments) (27 reactions) (0 assignees)C++ (2,005 forks)batch import
enhancementhelp wanted

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Description

This is a question of documentation rather than an issue. I can't find any example of the following very common scenario:

std::vector<int> some_func();
...
// We want to expose returned std::vector as a numpy array without copying
m.def("some_func", []() -> py::array {
   auto data = some_func();
   // What to do with data?? Map it with Eigen (then return what?), wrap somehow with py::buffer (how?)
})

I don't know the answer. It would be very nice to have this explained in docs since this scenario if rather common.

Contributor guide

Research direction
Search pybind11 documentation and examples for converting std::vector to py::array without copying. Look at py::array t and py::buffer info usage. Check if there are existing tests or snippets showing buffer protocol integration.
Tech stack
cpppython
Domain
documentation
Issue type
Documentation
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Python
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70