This is tutorial for having multiple version number of Python on OpenBSD it might be reproduced on other BSDs as well.
first create directory for having different versions being installed rather than operating system's default /usr/local/bin path.
the reason to do this is to avoid confliction with other packages on base operating system with system provided python.
1 mkdir /home/usr/miltipy && mkdir /home/usr/multipy/py2.7.10
now we will download desired python package and extract it.
2 wget https://path-to-python.2.7.10
extract downloaded package
3 tar -zxvf python-2.7.10.tgz
configure it to directory we created on first step
4 ./configure --prefix=/home/user/multipy/py2.7.10
then compile and install python2.7.10
5 make && make install
now using virtualenv we can now have python-2.7.10 for required project along side system provided python version (which on OpenBSD 5.9 as time of writing tutorial is python-2.7.11)
6 virtualenv -p /home/user/multipy/py2.7.10/bin/python-2.7.10 venv
now we can use python-2.7.10 for our required project.