Workable gettext

with_global.py

# workalendar/i18n.py

import gettext
import collections


_ = lambda x: x


def get_translation_for_language(language: str) -> gettext.Translations:
    return gettext.translation("mydomain", "/path/to/translations", [language])


def gettext(message:str) -> str:
    return translations[get_current_language()].gettext(message)


def ngettext(count: int, message: str) -> str:
    return translations[get_current_language()].ngettext(count, message)


def pgettext(context: str, message: str) -> str:
    # 3.8+ only :o
    return translations[get_current_language()].pgettext(context, message)

...

def get_current_language() -> str:
    # Do some magic: read a module variable or a threadlocal or a ContextVar or whatever. Your business.
    

def set_current_translation(language: str) -> None:
    # Do some magic: write a module variable or a threadlocal or a ContextVar or whatever. Your business.
    # a.k.a translation.activate    

@contextlib.contextmanager
def override_language(language: str):
    prev = get_current_language()
    set_current_language(language)
    try:
        yield
    finally:
        set_current_language(prev)

translations = collections.defaultdict(get_translation_for_language)

# workalendar/elsewhere.py

from workalendar.i18n import _, translate

holiday_name = _("Pâques")

def easter_name():
    set_current_language("fr")
    return gettext(holiday_name)
    #also works with
    with translation_override("de"):
        gettext("Pâques")
    # now back to french

without_global.py

# workalendar/i18n.py

import gettext
import collections


_ = lambda x: x


def get_translation_for_language(language: str) -> gettext.Translations:
    return gettext.translation("mydomain", "/path/to/translations", [language])


def translate(language: str, message:str) -> str:
    return translations[language].gettext(message)


def translate_count(language: str, count: int, message: str) -> str:
    return translations[language].ngettext(count, message)


def translate_context(language: str, context: str, message: str) -> str:
    # 3.8+ only :o
    return translations[language].pgettext(context, message)


translations = collections.defaultdict(get_translation_for_language)
  
# workalendar/elsewhere.py

from workalendar.i18n import _, translate

holiday_name = _("Pâques")

def easter_name(language):
    return translate(language, holiday_name)
    # or
    return translate(language, _("Pâques"))

note the following:

• You want to have gettext("string literals to translate") or _("string literals to translate") to appear somewhere in your code (for extraction purposes), but the translation should not occur at import time, which means either you'll need a gettext_lazy like django, or _() to be a no-op, what I did here
• Without global, you have to pass the language (that's kind of logic). This means the call to gettext cannot have the same signature as the original gettext, so I've chosen to give it a different name to make sure extraction is not confused

too bad for the defaultdict function. the function that's passed as a parameter doesn't accept arguments. I've found a way to make my own factory, though.
One step at a time...

Ah snap what I meant was actually a lru_cache ! If you lru_cache get_translation_for_language, then it would work (and you don't need the translation object anymore)

possibly. I think it'd be too early for caching stuff and such. What I'm trying to do at least (with a bit of success, right now, but it's late and I'm tired) is to get translations when language is known. It worked. I'm glad.

Premature optimisation is the root of all evil.

Hm, I think gettext.translation("mydomain", "/path/to/translations", [language]) is really not meant to be called multiple times...