From 71e29a7eba2924c5d5b2602c096b8b9e41210518 Mon Sep 17 00:00:00 2001
From: Tom de Geus <tom@geus.me>
Date: Fri, 28 May 2021 09:29:30 +0200
Subject: [PATCH] Adding CMake example with new findPython

---
 .github/workflows/ci.yml           | 51 ++++++++++++++++++++++++++++++
 14_cmake_findpython/CMakeLists.txt | 11 +++++++
 14_cmake_findpython/example.py     |  5 +++
 14_cmake_findpython/main.cpp       | 23 ++++++++++++++
 README.md                          |  8 +++++
 environment.yaml                   |  8 +++++
 6 files changed, 106 insertions(+)
 create mode 100644 .github/workflows/ci.yml
 create mode 100644 14_cmake_findpython/CMakeLists.txt
 create mode 100644 14_cmake_findpython/example.py
 create mode 100644 14_cmake_findpython/main.cpp
 create mode 100644 environment.yaml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..792f15f
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,51 @@
+name: CI
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+
+  standard:
+
+    strategy:
+      fail-fast: false
+      matrix:
+        runs-on: [ubuntu-latest, macos-latest, windows-latest]
+        example:
+          - 14_cmake_findpython
+
+    defaults:
+      run:
+        shell: bash -l {0}
+
+    name: "${{ matrix.example }} • ${{ matrix.runs-on }}"
+    runs-on: ${{ matrix.runs-on }}
+
+    steps:
+
+    - name: Basic GitHub action setup
+      uses: actions/checkout@v2
+
+    - name: Set conda environment
+      uses: mamba-org/provision-with-micromamba@main
+      with:
+        environment-file: environment.yaml
+        environment-name: myenv
+
+    - name: Configure
+      working-directory: ${{ matrix.example }}
+      run: cmake -Bbuild -DPython_EXECUTABLE=`which python`
+
+    - name: Compile
+      working-directory: ${{ matrix.example }}/build
+      run: cmake --build .
+
+    - name: Example
+      working-directory: ${{ matrix.example }}/build
+      run: |
+        cp ../example.py .
+        python example.py
diff --git a/14_cmake_findpython/CMakeLists.txt b/14_cmake_findpython/CMakeLists.txt
new file mode 100644
index 0000000..cb697d8
--- /dev/null
+++ b/14_cmake_findpython/CMakeLists.txt
@@ -0,0 +1,11 @@
+cmake_minimum_required(VERSION 3.18..3.20)
+
+project(mymodule)
+
+find_package(Python REQUIRED COMPONENTS Interpreter Development NumPy)
+find_package(pybind11 REQUIRED CONFIG)
+
+pybind11_add_module(mymodule main.cpp)
+target_link_libraries(mymodule PUBLIC pybind11::module Python::NumPy)
+
+target_compile_definitions(mymodule PRIVATE VERSION_INFO=0.1.0)
diff --git a/14_cmake_findpython/example.py b/14_cmake_findpython/example.py
new file mode 100644
index 0000000..6522b98
--- /dev/null
+++ b/14_cmake_findpython/example.py
@@ -0,0 +1,5 @@
+import mymodule
+import numpy as np
+
+A = (np.random.random([100]) * 100).astype(np.uint64)
+assert np.all(A * 2 == mymodule.foo(A))
diff --git a/14_cmake_findpython/main.cpp b/14_cmake_findpython/main.cpp
new file mode 100644
index 0000000..8f962bb
--- /dev/null
+++ b/14_cmake_findpython/main.cpp
@@ -0,0 +1,23 @@
+#include <vector>
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+
+namespace py = pybind11;
+
+template <class T>
+inline T foo(T& arg)
+{
+    T ret = arg;
+
+    for (auto& i : ret) {
+        i *= 2;
+    }
+
+    return ret;
+}
+
+PYBIND11_MODULE(mymodule, m)
+{
+    m.doc() = "Module description";
+    m.def("foo", &foo<std::vector<int>>, "Function description", py::arg("arg"));
+}
diff --git a/README.md b/README.md
index 071cbd9..1dd4c12 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,7 @@
     - [09_numpy_cpp-custom-matrix](#09_numpy_cpp-custom-matrix)
     - [10_enum](#10_enum)
     - [11_class-parent-child](#11_class-parent-child)
+    - [14_cmake_findpython](#14_cmake_findpython)
 
 <!-- /MarkdownTOC -->
 
@@ -265,3 +266,10 @@ This example contains a classical example where one or more classes are derived
 
 This particular case requires more involved interface, as is described in [the documentation](http://pybind11.readthedocs.io/en/stable/advanced/classes.html).
 
+## [14_cmake_findpython](14_cmake_findpython)
+
+This example features the use of the new *FindPython* in *CMake*.
+In order to use it with *pybind11* one should take care to:
+
+1.  Call `find_package(Python REQUIRED COMPONENTS Interpreter Development ...)` before  `find_package(pybind11 REQUIRED)`.
+2.  Using the command-line `cmake ... -DPython_EXECUTABLE=\`which python\`` to for *CMake* to use a specific *Python* version. 
diff --git a/environment.yaml b/environment.yaml
new file mode 100644
index 0000000..1ee036d
--- /dev/null
+++ b/environment.yaml
@@ -0,0 +1,8 @@
+channels:
+  - conda-forge
+dependencies:
+  - cmake
+  - make
+  - pybind11
+  - python
+  - numpy