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Thanks mate! (BTW: Indenting code with four spaces makes HN format it like code.) So the thing I'm still not getting from your example is allowing the template

• ratorx 2y ago
  template1 is a function that takes in a parameter evil (with a SanitisedString type that wraps a regular str) and returns the fully expanded str. It is implemented by just returning an f-string equivalent to the t-string in your example. Same with template2. Using the SanitisedString type forces the user to explicitly call a sanitiser function that returns a SanitisedString and prevents them from passing in an unsanitised str.
  • itishappy 2y ago
    You're just handing off responsibility for sanitization to the user instead of the library author. With t-strings the rendering function is responsible for sanitization, and users can pass unrendered templates to it. With f-strings there's no concept of an unrendered template, it just immediately becomes a string. Whoever is creating the template therefore has to be careful what they put in it.