index suggestions #49

This item suggests a few specific additions to the index. I realize indexing is a complex topic, and creating a comprehensive index requires both technical knowledge and indexing skills. This issue probably scratches only the surface of a big topic, but I suggest the following as starting points.

• Page 154, middle of the page, definition of __repr__. I couldn't remember the meaning of !r in f'Account({self.owner!r} ...)'. Suggest adding ! to the index, linking it to the explanations of !r and !s on page 252. There might be other meanings of ! to include.
• Suggest adding index entry for variables, expansion in strings. Possibly "see f-strings"
• Suggest adding index entry for expansion, variables in strings. Possibly "see f-strings"
• Suggest adding index entry for interpolation, variables in strings. Possibly "see f-strings"
• Suggest adding sub-entry to format() method: "see also f-strings"