rustfluent

A Python interface to the Rust Fluent Library.

This project is a small shim around fluent-rs, so it can be used from Python.

Warning

This package is under active development, and breaking changes may be released at any time. Be sure to pin to specific versions if you're using this package in a production environment.

Prerequisites

This package supports:

• Python 3.11
• Python 3.12

Installation

pip install rustfluent

Usage

import rustfluent

# First load a bundle
bundle = rustfluent.Bundle(
    "en",
    [
        # Multiple FTL files can be specified. Entries in later
        # files overwrite earlier ones.
        "en.ftl",
    ],
)

# Fetch a translation
assert bundle.get_translation("hello-world") == "Hello World"

# Fetch a translation that includes variables
assert bundle.get_translation("hello-user", variables={"user": "Bob"}) == "Hello, \u2068Bob\u2069"

The Unicode characters around "Bob" in the above example are for Unicode bidirectional handling.

API reference

Bundle class

A set of translations for a specific language.

import rustfluent

bundle = rustfluent.Bundle(
    language="en-US",
    ftl_files=[
        "/path/to/messages.ftl",
        "/path/to/more/messages.ftl",
    ],
)

Parameters

Name	Type	Description
language	str	Unicode Language Identifier for the language.
ftl_files	list[str]	Full paths to the FTL files containing the translations. Entries in later files overwrite earlier ones.
strict	bool, optional	In strict mode, a ParserError will be raised if there are any errors in the file. In non-strict mode, invalid Fluent messages will be excluded from the Bundle.

Raises

• FileNotFoundError if any of the FTL files could not be found.
• rustfluent.ParserError if any of the FTL files contain errors (strict mode only).

Bundle.get_translation

>>> bundle.get_translation(identifier="hello-world")
"Hello, world!"
>>> bundle.get_translation(identifier="hello-user", variables={"user": "Bob"})
"Hello, \u2068Bob\u2069!"
>>> bundle.get_translation(identifier="hello-user", variables={"user": "Bob"}, use_isolating=False)
"Hello, Bob!"

Parameters

Name	Type	Description
identifier	str	The identifier for the Fluent message.
variables	dict[str, str | int | datetime.date], optional	Any variables to be passed to the Fluent message.
use_isolating	bool, optional	Whether to insert Unicode Directionality Isolation Marks around placeables, to indicate that their direction may differ from the surrounding message. Defaults to True.

Supported variable types:

• str: Rendered as-is.
• int: Must be in the range -2,147,483,648 to 2,147,483,647. Rendered as-is.
• datetime.date: Rendered in the form YYYY-MM-DD.

Return value

str: the translated message.

If there is a problem with a passed variable (e.g. it is of the wrong type or an integer that is larger than a signed long integer), then the name of the variable will be used instead.

Raises

• ValueError if the message could not be found or has no translation available.
• TypeError if a passed variable name (i.e. a key in the variables dict) is not a string.

Contributing

See Contributing.