Document the thousands separator.
diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index e887021..2c000b0 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -300,7 +300,7 @@
The general form of a *standard format specifier* is:
.. productionlist:: sf
- format_spec: [[`fill`]`align`][`sign`][#][0][`width`][.`precision`][`type`]
+ format_spec: [[`fill`]`align`][`sign`][#][0][`width`][,][.`precision`][`type`]
fill: <a character other than '}'>
align: "<" | ">" | "=" | "^"
sign: "+" | "-" | " "
@@ -358,6 +358,10 @@
hexadecimal output. If present, it specifies that the output will be prefixed
by ``'0b'``, ``'0o'``, or ``'0x'``, respectively.
+The ``','`` option signals the use of a comma for a thousands separator.
+For a locale aware separator, use the ``'n'`` integer presentation type
+instead.
+
*width* is a decimal integer defining the minimum field width. If not
specified, then the field width will be determined by the content.