PEP 501: (reopen) General purpose string template literals

[guido (Guido van Rossum)]

@kknechtel

It would be nice to be able to leverage some of this architecture to create t-strings with deferred evaluation at runtime: i.e., a way to convert a string (not necessarily literal!) like "Logger: {record.name}; Event: {event}; Details: {data}" explicitly at runtime into a TemplateLiteral instance equivalent to t"Logger: {'record.name'}; Event: {'event'}; Details: {'data'}". That would be huge for i18n purposes, for example: we could read the template string from a l10n resource bundle.

The more general tag-string proposal at GitHub - jimbaker/tagstr: This repo contains an issue tracker, examples, and early work related to PEP 999: Tag Strings should be able to do that. The tag function there receives both a lambda that, when called, returns the value of the expression, and a string that represents the text of the expression. (And also the conversion code and the format spec, if present.)