Does Office 365 have an API that does what Google Sheets v3 did? Google is legendary for killing products -- even beloved and successful ones: RIP, Reader -- while Microsoft has OCD about supporting APIs that are 30 years old.
I had been looking at using APIs and automation with G-Suite but was always a little nervous to tie my apps to the whims of Google. This is another example of why I shouldn't entertain that thought and use "old, boring technology" like offline spreadsheets (like Libre Office docs) or Office 365 instead.
>Microsoft has OCD about supporting APIs that are 30 years old
That was the old Microsoft, for all its faults. The new Microsoft is much more Google-like: products are chucked out and then killed shortly after if they get no traction. They deprecate and remove services with ruthless regularity even when they are considered first-rate - like Lync/SkypeForBusiness.
I looked into the a while ago. There are some other options but the only ones that appear to be fairly robust are manipulation from either Microsoft Flow or Powerapps. Both of which are sort of "citizen development" visual type environments.
Heads up on the Microsoft Graph API: it only works for certain styles of Microsoft Office customer. In particular, you can only authenticate against it with Azure AD, which completely chokes out the home market.
That is not true. There are certain APIs only applicable to commercial users, but the same Graph API calls (for example against OneDrive or Excel) can be used across both.
Is that new? The post I linked to, from 9/2019, says "Support for workbooks stored in OneDrive Consumer platform is still not available. At this time, only the files stored in business platform is supported by Excel REST APIs."
Last time I checked, Microsoft had nothing like the Sheets API. However, since then, as the sister comment points out, they have published the Graph API (https://docs.microsoft.com/en-us/graph/api/overview?toc=./re...), which seems to have a pretty decent set of spreadsheet API methods.
Google's spreadsheet API is very powerful, and contrary to the spirit of the OP, I think the update largely preserves existing functionality (the developer may need to adjust their thinking and be aware of other aspects/patterns of Google APIs). I'm actually very glad they came out with v4, as during the lifetime of v3 it was not entirely clear whether they would be updating it further.
Offline spreadsheets are completely unusable for most of the use cases that these APIs enable. The biggest value add of the online spreadsheet APIs is to be able to integrate with relevant online data sources to dynamically update the spreadsheet contents, provide typeahead suggestions/autocompletions, or sync data with another system. This can be very powerful because it immediately brings the full power of spreadsheets to the user interface of your data system, without having to build something equivalent to a spreadsheet interface yourself (which, contrary to some loud opinions out there, can be a huge win in business applications by enabling non-technical or partially technical users to be more flexible, more productive, and less dependent on other members of the organization to do their work).
Until the graph API, the closest thing to a spreadsheet API provided by a Google competitor was... VBA. Visual Basic for Applications. That is still the main API for desktop Office applications. Good luck using that. I just about gouged my eyes out the last time I tried to use it.
I had been looking at using APIs and automation with G-Suite but was always a little nervous to tie my apps to the whims of Google. This is another example of why I shouldn't entertain that thought and use "old, boring technology" like offline spreadsheets (like Libre Office docs) or Office 365 instead.