>Would you expect that a user input like "{secret} please" is interpolated?

That's basically what the recent log4j security vulnerability was all about. "Helpfully" interpolating logs by default.

Look up how this works in Swift. They only have one string. No raw strings or f strings. Yet they have all the power of all three python string types and less syntax. It's very nice.

Swift does have raw strings (the #"extended delimiter"# syntax).

No. Those ALSO have string interpolation!

#"\#(expression)"#

That is exactly the point.

But they’re a distinct string syntax. Your point seemed to be that there was only one. rf"{expression}" works in Python too, note, so either way you want to interpret it, raw strings aren’t a difference.

No, they aren't. You can have any number of #. Including zero. It's ONE syntax.

If you only make it work with string literals (e.g. generate the underlying formatting logic at parse time), it wouldn't allow arbitrary inputs to be treated as f strings.

The assumption I'm thinking they mean is to make formatting default and unformatted not default, for example, how "raw" strings were treated, escaped characters are replaced with the ascii code by default unless the string is raw, signified by an 'r' prefixed in front.

Adding that behavior would break existing code that uses str.format, and Python tries to avoid breaking code between minor releases.