Unicode RBNF

A pure Python implementation of rule based number formatting (RBNF) using the Unicode Common Locale Data Repository (CLDR).

This lets you spell out numbers for a large number of locales:

from unicode_rbnf import RbnfEngine

engine = RbnfEngine.for_language("en")
assert engine.format_number(1234).text == "one thousand two hundred thirty-four"

Different formatting purposes are supported as well, depending on the locale:

from unicode_rbnf import RbnfEngine, FormatPurpose

engine = RbnfEngine.for_language("en")
assert engine.format_number(1999, FormatPurpose.CARDINAL).text == "one thousand nine hundred ninety-nine"
assert engine.format_number(1999, FormatPurpose.YEAR).text == "nineteen ninety-nine"
assert engine.format_number(11, FormatPurpose.ORDINAL).text == "eleventh"

For locales with multiple genders, cases, etc., the different texts are accessible in the result of format_number:

from unicode_rbnf import RbnfEngine

engine = RbnfEngine.for_language("de")
print(engine.format_number(1))

Result:

FormatResult(
  text='eins',
  text_by_ruleset={
    'spellout-numbering': 'eins',
    'spellout-cardinal-neuter': 'ein',
    'spellout-cardinal-masculine': 'ein',
    'spellout-cardinal-feminine': 'eine',
    'spellout-cardinal-n': 'einen',
    'spellout-cardinal-r': 'einer',
    'spellout-cardinal-s': 'eines',
    'spellout-cardinal-m': 'einem'
  }
)

The text property of the result holds the text of the ruleset with the shortest name (least specific).

Supported locales

See: https://github.com/unicode-org/cldr/tree/release-44/common/rbnf

Engine implementation

Not all features of the RBNF engine are implemented. The following features are available:

• Literal text (hundred)
• Quotient substitution (<< or ←←)
• Reminder substitution (>> or →→)
• Optional substitution ([...])
• Rule substituton (←%ruleset_name←)
• Rule replacement (=%ruleset_name=)
• Special rules:
  • Negative numbers (-x)
  • Improper fractions (x.x)
  • Not a number (NaN)
  • Infinity (Inf)

Some features that will need to be added eventually:

• Proper fraction rules (0.x)
• Preceding reminder substitution (>>> or →→→)
• Number format strings (==)