PEP 501: Explicit note regarding prerendering templates

pep-0501.txt

@@ -462,6 +462,17 @@ Since the proposed operator is useful without binary interpolation support, and
 such support can be readily added later, further consideration of binary
 interpolation is considered out of scope for the current PEP.
 
+Interoperability with str-only interfaces
+-----------------------------------------
+
+For interoperability with interfaces that only accept strings, interpolation
+templates can be prerendered with ``str``, rather than delegating the rendering
+to the called function.
+
+This reflects the key difference from PEP 498, which *always* eagerly applies]
+the default rendering, without any convenient way to decide to do something
+different.
+
 Preserving the raw template string
 ----------------------------------