Why did pip upgrade from version 10 to version 18?

Question

while running a pip install script I get the following warning:

 You are using pip version 10.0.1, however version 18.0 is available

Answer 1

First point in the release notes:

• Switch to a Calendar based versioning scheme.

https://pip.pypa.io/en/stable/news/

More about calendar versioning: https://calver.org/