Is Data Warehousing possible in MySQL and PostgresSQL
You can certainly use MySQL or PostgreSQL for this requirement using Python as your database access language. I've never used Python cubes so I can't speak to that.
I would recommend that you use PostgreSQL - it has windowing functions and CTEs (common table expressions). It also supports CHECK CONSTRAINTs and a full range of set operators.
MySQL is reasonably good for read heavy OLTP database loads but little else.
PostgreSQL is superior for analytical work (DW - data warehousing, or OLAP) while at the same time being an excellent all-rounder in the OLTP arena.
This is a very broad answer, but that is because the question is very broad, too.
MySQL has never been focused on OLAP, for one particular reason, its main engine, InnoDB, and MySQL cluster (NDB) are optimised for OLTP loads. Doing analytical queries is usually slow because it involves reading lots of rows.
That does not mean that you could not do OLAP on MySQL, there are some people suggesting options for doing that in MySQL with database structure changes. There are also pluggable specialised engines and connectors that may or may not be helpful depending on your expected queries, like InfiniDB or Impala.
Having said that, you can search for alternative database engines that may be suitable for your needs.