Python's string format is also very similar to the "double mustache" convention widely used in web development. The following template string: "I have {{ap

Python's string format is also very similar to the "double mustache" convention widely used in web development. The following template string: "I have {{apples}} apples" To my certain knowledge this works in Jinja2, Django templates, Vue.js, mustache.js, handlebars.js, and probably many others. PEP 498 mentions that they did look at other languages to see what was supported: https://www.python.org/dev/peps/pep-0498/#similar-support-in-other-languages https://www.python.org/dev/peps/pep-0498/#similar-support-in... And they link to this Wikipedia article, which lists many examples: https://en.wikipedia.org/wiki/String_interpolation https://en.wikipedia.org/wiki/String_interpolation Scanning through that, my impression is that "there is nothing new under the sun" and aside from an occasional "$" or "#" prefix, or a willfully arbitrary deviation like ColdFusion, the conventions can all be traced the Bourne shell /bin/sh/ which was released in 1979. Prior to that, the prinf() syntax was presumably the most common, but it's obscure. Does anyone know if the ${variable} convention was original with the Bourne shell, or if it can be traced back further?