update to python 3.7 using anaconda
This can be installed via conda with the command conda install -c anaconda python=3.7 as per https://anaconda.org/anaconda/python.
Though not all packages support 3.7 yet, running conda update --all may resolve some dependency failures.
Python 3.7 is now available to be installed, but many packages have not been updated yet. As noted by another answer here, there is a GitHub issue tracking the progress of Anaconda building all the updated packages.
Until someone creates a conda package for Python 3.7, you can't install it. Unfortunately, something like 3500 packages show up in a search for "python" on Anaconda.org (https://anaconda.org/search?q=%22python%22) so I couldn't see if anyone has done that yet.
You might be able to build your own package, depending on what OS you want it for. You can start with the recipe that conda-forge uses to build Python: https://github.com/conda-forge/python-feedstock/
In the past, I think Continuum have generally waited until a stable release to push out packages for new Pythons, but I don't work there, so I don't know what their actual policy is.