Error in Format Specification Mini-Language concerning precision_with_grouping in 3.14

Documentation

On this page: https://docs.python.org/3.14/library/string.html#grammar-token-format-spec-format_spec

format_spec:             [options][width_and_precision][type]
options:                 [[fill]align][sign]["z"]["#"]["0"]
fill:                    <any character>
align:                   "<" | ">" | "=" | "^"
sign:                    "+" | "-" | " "
width_and_precision:     [width_with_grouping][precision_with_grouping]
width_with_grouping:     [width][grouping]
precision_with_grouping: "." [precision][grouping]
width:                   digit+
precision:               digit+
grouping:                "," | "_"
type:                    "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g"
                         | "G" | "n" | "o" | "s" | "x" | "X" | "%"

The precision_with_grouping syntaxe is wrong, because it accepts . without precision or grouping. But

>>> f'{1234.1234:.f}'
Traceback (most recent call last):
  File "<python-input-17>", line 1, in <module>
    f'{1234.1234:.f}'
      ^^^^^^^^^^^^^^
ValueError: Format specifier missing precision

(The error does not mention grouping either)

The right syntax should be

precision_with_grouping: "." precision [grouping] | "." grouping

Linked PRs

@skirpichev

cc @skirpichev This is something we did right? I don't remember the issue/PR

@jonathanpoelen

Yes, it's not accurate, see #125304 (review). I forgot that, lets fix this.

@jonathanpoelen, would you like to propose a pr?

I'll let you do the pr :)

pythongh-134449: fix grammar for precision_with_grouping in format de…

PR is ready to review: #134608

gh-134449: fix grammar for `precision_with_grouping` in format descri…

pythongh-134449: fix grammar for `precision_with_grouping` in format …

[3.14] gh-134449: fix grammar for `precision_with_grouping` in format…

#132205 was created before and was slightly better. Anyway, this is closed.

pythongh-134449: fix grammar for `precision_with_grouping` in format …

Navigation Menu

Repository navigation

Error in Format Specification Mini-Language concerning `precision_with_grouping` in 3.14 #134449

Documentation

Linked PRs

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Error in Format Specification Mini-Language concerning precision_with_grouping in 3.14 #134449

Description

Documentation

Linked PRs

Activity

picnixz commented on May 23, 2025

skirpichev commented on May 23, 2025

jonathanpoelen commented on May 24, 2025

skirpichev commented on May 25, 2025

skirpichev commented on Jun 24, 2025

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions

Error in Format Specification Mini-Language concerning `precision_with_grouping` in 3.14 #134449