How to link with Python3 Libs with cmake?

Question

I have Python3 installed via brew install python3. However, cmake cannot find PythonLibs 3. Here's the header of my CMakeLists.txt.

cmake_minimum_required(VERSION 3.0)
find_package(PythonLibs 3 REQUIRED)

When I ran cmake, I got this error message

Could NOT find PythonLibs: Found unsuitable version "2.7.6", but required is at least "3" (found /usr/lib/libpython2.7.dylib)

Not sure what I did wrong.

Solution 1

In my experience, this happened because I was using an older version of cmake (2.8 instead of 3+) that didn't know about Python 3.4 (it gave up after 3.3.)

The solution was to go into the CMakeLists.txt file and add an "additional versions" directive ABOVE the find_package:

set(Python_ADDITIONAL_VERSIONS 3.4) find_package(PythonLibs 3 REQUIRED)

You could probably also fix it by upgrading your version of cmake. But the above worked for me with cmake 2.8

Solution 2

Because you are using CMake >= 3.0, you can you find_package(Python COMPONENTS Interpreter Development) see: https://cmake.org/cmake/help/v3.12/module/FindPython.html

That would for instance give you for:

find_package(Python COMPONENTS Interpreter Development)

message("Python_FOUND:${Python_FOUND}")
message("Python_VERSION:${Python_VERSION}")
message("Python_Development_FOUND:${Python_Development_FOUND}")
message("Python_LIBRARIES:${Python_LIBRARIES}")

Results:

Python_FOUND:TRUE
Python_VERSION:3.8.0
Python_Development_FOUND:TRUE
Python_LIBRARIES:/usr/lib/x86_64-linux-gnu/libpython3.8.so