Flask Babel

---

1. Basic Internationalization (I18n) with Flask-Babel

from flask import Flask, render_template
from flask_babel import Babel

app = Flask(__name__)
babel = Babel(app)

@babel.localeselector
def get_locale():
    return request.accept_languages.best_match(["en", "fr"])

@app.route("/")
def index():
    return render_template("index.html")

2. Set Default Locale

babel.default_locale = "en"

3. Automatic Contextualization

with app.test_request_context():
    get_locale() == "en"

4. Get Current Locale

from flask_babel import get_locale

get_locale() == "en"

5. Get List of Available Locales

from flask_babel import get_available_locales

get_available_locales() == ["en", "fr"]

6. Set Default Timezone

babel.default_timezone = "UTC"

7. Automatic Contextualization (Timezones)

with app.test_request_context():
    get_timezone() == "UTC"

8. Get Current Timezone

from flask_babel import get_timezone

get_timezone() == "UTC"

9. Get List of Available Timezones

from flask_babel import get_available_timezones

get_available_timezones() == ["UTC", "America/New_York"]

10. Custom Locale Selector

@babel.localeselector
def get_locale():
    cookie = request.cookies.get("lang")
    if cookie in ["en", "fr"]:
        return cookie
    return request.accept_languages.best_match(["en", "fr"])

11. Using the gettext Function

from flask_babel import gettext

gettext("Hello") == "Bonjour"

12. Using the ngettext Function (Pluralization)

from flask_babel import ngettext

ngettext("apple", "apples", 2) == "2 apples"

13. Using Lazy Translation Objects

from flask_babel import lazy_gettext

translation = lazy_gettext("Hello")
str(translation) == "Bonjour"

14. Using the translate Filter in Templates

<div data-gb-custom-block data-tag="trans" data-0='Hello'></div>

 == "Bonjour"

15. Using the ngettext Filter in Templates (Pluralization)

<div data-gb-custom-block data-tag="trans" data-0='apples' data-n='2'></div>

 == "2 apples"

16. Lazy Translation Objects in Templates

<div data-gb-custom-block data-tag="trans" data-0='Hello' data-1='Hello'></div>

 == "Bonjour"

17. Custom Translation Functions

babel.add_domain("messages")

@babel.localeselector
def get_lang():
    return request.cookies["lang"]

@babel.domain_selector
def get_domain():
    return "messages"

18. Translations in Different Files

babel.messagespath = ["/path/to/translations", "/path/to/fallback"]

19. Using the lazy_gettext Function in Forms

from flask_wtf import FlaskForm
from wtforms.fields import StringField
from flask_babel import lazy_gettext

class MyForm(FlaskForm):
    name = StringField(lazy_gettext("Name"))

20. Translations in Forms with Validation Messages

class MyForm(FlaskForm):
    name = StringField(
        lazy_gettext("Name"),
        validators=[validators.Required(lazy_gettext("Name is required."))]
    )

21. Automatic Translation Context in Forms

with app.test_request_context("/fr"):
    f = MyForm()
    f.name.label.text == "Nom"

22. Flask-WTForms Integration with Lazy Translation

class MyForm(Form):
    name = StringField(lazy_gettext("Name"), render_kw={"placeholder": lazy_gettext("Enter your name")})

23. Flask-Admin Integration

from flask_admin import Admin, BaseView

class MyView(BaseView):
    @babel.localeselector
    def get_locale(self):
        return request.args.get("lang")

24. Jinja2 Integration

<div data-gb-custom-block data-tag="if" data-0='en' data-1='en'>

    English content

<div data-gb-custom-block data-tag="elif" data-0='fr' data-1='fr'></div>

    French content

</div>

25. Flask-Script Integration

from flask_script import Manager

manager = Manager(app)

@manager.command
def translate():
    from flask_babel import compile_catalog
    compile_catalog(app.config["BABEL_COMPILE_CATALOG"])

26. Loading Translations from Files

from os import path

babel.load_translations(
    path.abspath(path.join(path.abspath(path.dirname(__file__)), "../translations"))
)

27. Using Translations from Different Directories

babel.messagespath = ["/path/to/translations", "/path/to/fallback"]

28. Get the Translation for a Specific Domain

from flask_babel import gettext

gettext("Hello", domain="messages") == "Bonjour"

29. Translation Extensibility

class MyTemplate(MTSafeTemplate):
    def __getitem__(self, key):
        translation = gettext(key)
        if translation != key:
            return translation
        return super().__getitem__(key)

30. Using Translations with String Formatting

from flask_babel import gettext

gettext("Hello %s", "Alice") == "Hello Alice"

31. Dynamic Translation Context

with app.test_request_context("/fr?foo=bar"):
    gettext("Hello") == "Bonjour"

32. Setting Locale in the Query String

@babel.localeselector
def get_locale():
    return request.args.get("lang")

33. Translation for Multiple Languages

babel.available_languages = ["en", "fr", "es"]

34. Using Translations in SQL Queries

from flask_babel import get_sqlalchemy_connector

db.engine.dialect.connector = get_sqlalchemy_connector()

35. Custom Timezone Selector

@babel.timezoneselector
def get_timezone():
    return request.cookies.get("tz")

36. Using the Render Function to Format Dates

from flask_babel import render_template

render_template("date.html", date=datetime.utcnow())