Added some examples from Python's source. Both 'before' (str.format) and 'after' (f-strings).

pep-0498.txt

@@ -551,6 +551,35 @@ If you feel you must use lambdas, they may be used inside of parens::
   >>> f'{(lambda x: x*2)(3)}'
   '6'
 
+Examples from Python's source code
+==================================
+
+Here are some examples from Python source code that currently use
+str.format(), and how they would look with f-strings. This PEP does
+not recommend wholesale converting to f-strings, these are just
+examples of real-world usages of str.format() and how they'd look if
+written from scratch using f-strings.
+
+Lib/asyncio/locks.py::
+
+  extra = '{},waiters:{}'.format(extra, len(self._waiters))
+  extra = f'{extra},waiters:{len(self._waiters)}'
+
+Lib/configparser.py::
+
+  message.append(" [line {0:2d}]".format(lineno))
+  message.append(f" [line {lineno:2d}]")
+
+Tools/clinic/clinic.py::
+
+  methoddef_name = "{}_METHODDEF".format(c_basename.upper())
+  methoddef_name = f"{c_basename.upper()}_METHODDEF"
+
+python-config.py::
+
+  print("Usage: {0} [{1}]".format(sys.argv[0], '|'.join('--'+opt for opt in valid_opts)), file=sys.stderr)
+  print(f"Usage: {sys.argv[0]} [{'|'.join('--'+opt for opt in valid_opts)}]", file=sys.stderr)
+
 References
 ==========