Making a spreadsheet that does a variety of calculations, displays graphs, live updates, is share-able, editable via web and mobile, can be embedded in technical documents and presentations is all free with a spreadsheet. Your comment trying to address the speed argument, replacing with a "python REPL" is difficult to take seriously. Spreadsheets are order of magnitude faster, and that speed advantage scales from the simplest of spreadsheets to the most complex (i.e., just summing a column of data will be maybe 10 times faster in a spreadsheet than a python REPL [although both are trivially fast for this use case], and doing all of the above listed features would be months to program relative to free for the spreadsheet).
