This tag is used to indicate both which Python implementation a package requires (if any), as well as the version require.
The tag is made up of two portions that describe this relationship.
Python projects with source code tags take the following form:

• Final one or two qualities are the Major as well as Minor version of its performance. 
• The first two characters contain a Python implementation description, followed by a dash as well as the version of it’s need.
• Brood (as wheel) use the Major as well as Minor version of the Python language that the performance provides.

When requesting list or index, this tag of the target runtime must be provided.

This is to ensure that the index returned contains only packages that will work on the target runtime.

For Python projects with source code click here