As of 19th July 2018, Google Cloud Functions supports Python 3.7.
Kindly check the Runtime environment to find the Python 3.7 runtime and sample script (based on Flask) .
--UPDATED--
Official Documentation for the Google Cloud Functions - Python 3.7 support Beta Release.
This is a beta release of the Python runtime for Google Cloud
Functions. This feature might be changed in backward-incompatible ways
and is not subject to any SLA or deprecation policy.
SkLearn, Numpy is supported in Google Cloud function. Also I've run a sample test to confirm the availability of Pandas as well and its working fine.
https://github.com/mkanchwala/google-functions-python-example
Hope this helps to all the "Py" lovers.