How To Fix “CMake can not find PythonLibs” Error on Ubuntu

If you’re working with CMake on Ubuntu, you may encounter the error “CMake cannot find PythonLibs”. This error can be frustrating, especially when you’re in the middle of a project. However, don’t fret! This article will guide you through several solutions to fix this issue.

Understanding the Error

Before we delve into the solutions, it’s important to understand what the error means. CMake is a cross-platform build system that uses scripts to control the software’s build process, in a compiler-independent manner. When CMake can’t find PythonLibs, it means it’s unable to locate the necessary Python libraries for building your software.

Solution 1: Install python-dev

The first solution to this problem is installing the python-dev package. This package contains the header files you need to build Python extensions.

You can install python-dev by running the following command in your terminal:

sudo apt-get install python-dev

In this command, sudo allows you to run commands with the security privileges of the superuser, while apt-get install is used to install packages.

After running this command, try building your software again to see if the issue has been resolved.

Solution 2: Specify Python Version

If you have multiple versions of Python installed on your system, CMake may be struggling to find the correct version. In this case, you can specify the Python version in your CMakeLists.txt file.

For instance, if you want to specify Python version 3.4, add the following lines before the find_package statement:

set(Python_ADDITIONAL_VERSIONS 3.4)

In this command, set is a CMake command that sets a variable to a value, Python_ADDITIONAL_VERSIONS is the variable we’re setting, and 3.4 is the value we’re setting it to.

Solution 3: Clear CMake Cache

Sometimes, the problem might be due to a cached configuration. In this case, you can try removing the CMake cache file (CMakeCache.txt) and then rerun CMake.

To remove the CMake cache file, run the following command in your terminal:

rm CMakeCache.txt

In this command, rm is a command that removes files or directories, and CMakeCache.txt is the file we’re removing.

After removing the cache, rerun CMake. It will perform a fresh configuration and might be able to find the PythonLibs.

Solution 4: Update CMake Version

If none of the above solutions work, you might be using an outdated version of CMake that doesn’t support the Python version installed on your system.

Starting from CMake 3.0, it supports searching up to Python 3.4. You can download the latest version of CMake from the official website and install it manually.

Conclusion

The “CMake cannot find PythonLibs” error can be a roadblock in your software development process, but it’s not insurmountable. By following the solutions outlined in this article, you should be able to resolve the issue and get back to your project. Remember to try these solutions one by one and test if the issue is resolved after each step. Happy coding!

set(Python_ADDITIONAL_VERSIONS 3.4)