Improve the F-strings and format specifier documentation (GH-4931) (GH-4933)

Mention that the format-specifier mini language in f-strings
is the same one used by str.format.
(cherry picked from commit f4e21a2a72f76d75a6cc6f74faf910a5f3108482)

diff --git a/Doc/reference/lexical_analysis.rst b/Doc/reference/lexical_analysis.rst
index 30dc72184ae28614bdb69832afece63257e1a671..c0f2ee59b8c2c32a6a2246054b6a7e02031bfb72 100644 (file)
--- a/Doc/reference/lexical_analysis.rst
+++ b/Doc/reference/lexical_analysis.rst
@@ -654,10 +654,11 @@ expression or conversion result.  An empty string is passed when the
 format specifier is omitted.  The formatted result is then included in
 the final value of the whole string.
 
-Top-level format specifiers may include nested replacement fields.
-These nested fields may include their own conversion fields and
-:ref:`format specifiers <formatspec>`, but may not include more
-deeply-nested replacement fields.
+Top-level format specifiers may include nested replacement fields. These nested
+fields may include their own conversion fields and :ref:`format specifiers
+<formatspec>`, but may not include more deeply-nested replacement fields. The
+:ref:`format specifier mini-language <formatspec>` is the same as that used by
+the string .format() method.
 
 Formatted string literals may be concatenated, but replacement fields
 cannot be split across literals.