I have 2 versions of python installed, but cmake is using older version. How do I force cmake to use the newer version?
PythonPython 2.7CmakePython Problem Overview
I have 2 versions of python installed, but cmake is using older version. How do I force cmake to use the newer version?
Python Solutions
Solution 1 - Python
You may try either of these depending on what you need:
For CMake >= 3.12
According to the changelog:
> New "FindPython3" and "FindPython2" modules, as well as a new
> "FindPython" module, have been added to provide a new way to locate
> python environments.
find_package(Python COMPONENTS Interpreter Development)
Docs: > This module looks preferably for version 3 of Python. If not found, > version 2 is searched. To manage concurrent versions 3 and 2 of > Python, use FindPython3 and FindPython2 modules rather than this one.
For CMake < 3.12
Docs:
find_package(PythonInterp 2.7 REQUIRED)
find_package(PythonLibs 2.7 REQUIRED)
Solution 2 - Python
Try to add -DPYTHON_EXECUTABLE:FILEPATH=/path/to/python2.7
It might be a path problem?
Also could specify the path to your python library,use your version that you want:
cmake -DPYTHON_LIBRARIES=/Library/Frameworks/Python.framework/Versions/2.7/lib/libpython2.7.dylib .
Solution 3 - Python
I had a similar problem, and resolved it using Paul's answer as a hint. I needed to use python2.7 to compile an older library, but cmake keeps picking up my python3.2 libraries (and executable).
First, I ran cmake with default options, then edited the CMakeCache.txt file which it generated. I did it this way primarily because I didn't know the proper -D... incantations to cause cmake to get the python library and include paths, etc right in the first place.
In my CmakeCache.txt, I found lines like this
-
Path to a program
PYTHON_EXECUTABLE:FILEPATH=/usr/bin/python -
Path to a directory
PYTHON_INCLUDE_DIR:PATH=/usr/include/python3.2 -
Path to a library
PYTHON_LIBRARY:FILEPATH=/usr/lib/libpython3.2.so
And replaced every occurrence of python3.2 with python2.7. I also had to rename the PYTHON_EXECUTABLE to use python2.7, since python is a symlink to python3.2 on my system.
Then I reran cmake. Because it prefers its cached values to actually looking for the libraries, this should work in all cases. At least, it did in mine.
Solution 4 - Python
I use anaconda(python 2.7.8) as well as python 2.7.6.
I tried -DPYTHON_EXECUTABLE:FILEPATH=$ANACONDA_HOME/bin, but version 1.4 found (weird:).
My solution is changing it to PYTHON_EXECUTABLE:
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -DBUILD_TIFF=ON \
-DPYTHON_LIBRARY=$ANACONDA_HOME/lib/libpython2.7.so \
-DPYTHON_INCLUDE_DIR=$ANACONDA_HOME/include/python2.7/ \
-DPYTHON_EXECUTABLE=$ANACONDA_HOME/bin/python
Solution 5 - Python
My use case was a rather large project in which C++ classes were made available to Python scripts via Boost.Python. After having fought the various quirks of CMake's Python interpreter and library detection, I finally gave up and rolled my own. My approach is based on a slightly after-edited version of the python-config script that is sometimes (but not always!) put into a newly created virtual environment (see this SO post on pyvenv for these issues, but I digress). This script is invoked by a small CMake snippet pyconfig.cmake. Both are freely available from the GitHub repo cmake-python-config.
Warning: The scripts assume that you have a Python 3 interpreter in your PATH. Detection of Python 2 is not attempted. The scripts do not attempt to find all installed versions of Python3 either.