The python ecosystem is really good here.

I do a lot of exploratory coding in ipython, though the threshold for "switch to a real editor and run git init and poetry new" is pretty low.

Want to munge CSV? stdlib, or pandas(https://pandas.pydata.org/pandas-docs/stable/)

Want to munge JSON? stdlib.

Want to munge a database? pandas, stdlib, anything that speaks sqlalchemy

Want to validate your json/sql/CSV/whatever and have it come in as a bunch of structured classes not std types? jsonschema https://pypi.org/project/jsonschema/, attrs+marshmallow, attrs+cattrs. http://www.attrs.org/en/stable/, https://desert.readthedocs.io/en/latest/ https://marshmallow.readthedocs.io/en/stable/ https://github.com/Tinche/cattrs

Want to transform csv into sqlite? https://github.com/simonw/csvs-to-sqlite

Want to serve sqlite as a REST api? https://datasette.readthedocs.io/en/stable/

Want to stuff simple things into a database really fast? https://dataset.readthedocs.io/en/latest/

Want to flip numerical data around? Numpy.https://docs.scipy.org/doc/numpy/reference/

Want to model it? Scipy https://www.scipy.org/docs.html, pandas

Want to plot it? seaborn https://seaborn.pydata.org/, plotnine https://plotnine.readthedocs.io/en/stable/

Want to futz around with structured data in a sensible way? glom https://glom.readthedocs.io/en/latest/, python-lenses https://github.com/ingolemo/python-lenses.

Want to spit out tabular data? Tabulate https://github.com/astanin/python-tabulate

Want to figure out where not to eat in chicago? built-ins: counter, defaultdict, comprehensions: https://www.youtube.com/watch?v=lyDLAutA88s

There's a LOT you can do pretty fast, and I can more or less hammer out a basic ETL cli script in my sleep at this point.