The general form of a *standard format specifier* is:
.. productionlist:: sf
- format_spec: [[`fill`]`align`][`sign`][#][0][`width`][`option`][.`precision`][`type`]
+ format_spec: [[`fill`]`align`][`sign`][#][0][`width`][`grouping_option`][.`precision`][`type`]
fill: <any character>
align: "<" | ">" | "=" | "^"
sign: "+" | "-" | " "
width: `integer`
- option: "_" | ","
+ grouping_option: "_" | ","
precision: `integer`
type: "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"