Installing a port to a specific python version

[Gerhard Schmidt]

Hi

I'm having a small problem with python and FreeBSD. I'm a python
developer. I Maintain some legacy code written in python2.7 and some new
projects in Python 3.6 and for testing purposes i need python 3.4 and
3.5. So I need all this versions of python on my system, at least to be
able to create virtual envs.

Installing the python interpreters is not a problem, but installing
python packages.

How can in say a port it shouldn't use the default version stated in
make.conf but a specific version. I don't want to change the default
version every time i install a Port.

I've tried to set PYTHON_VERSION as environment variable.
I've tried to give PYTHON_VERSION as parameter to make.
I've tried to give PYTHON as parameter to make.
I've tried python3.5 python35 3.5 and 35 with each of them, it still
installed the default python version.

Then i tried make PYTHON_DEFAULT=3.5 and get a error message.

So how can i tell a port to install the python3.5 version of a port
without changing the make.conf

Regards
  Estartu