The standard library documentation “6.1. string — Common string operations” describes string formatting through the `.format` method and the corresponding mini-language, and the `Template` class.  In the part describing the `Template` class (6.1.4) is the text:

> Instead of the normal %-based substitutions, Templates support $-based substitutions, using the following rules:

This is potentially confusing.  The documentation in this section has not made any mention of %-based substitutions.  Rather, a novel reader may, at this point, think that {}-based substitution is normal.  I would suggest to resolve this issue by simply not mentioning %-based substitutions, replacing the sentence above by:

> Templates support $-based substitutions, using the following rules: