I believe Lambda runs on AWS linux distributions, and 2.7 is the default Python version for those [1].<p>1.  <a href="https:&#x2F;&#x2F;aws.amazon.com&#x2F;amazon-linux-ami&#x2F;2015.03-release-notes&#x2F;" rel="nofollow">https:&#x2F;&#x2F;aws.amazon.com&#x2F;amazon-linux-ami&#x2F;2015.03-release-note...</a>