From e97e6c1d7d47a8007cc54bb78ee6ffaae8f69891 Mon Sep 17 00:00:00 2001
From: Dmitry Buslov <buslovdmitrij0@gmail.com>
Date: Sun, 16 Mar 2025 23:57:19 +0200
Subject: [PATCH 1/3] Feat: added i18 example (with dynamic translation)

---
 examples/i18n.py | 82 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 examples/i18n.py

diff --git a/examples/i18n.py b/examples/i18n.py
new file mode 100644
index 00000000..6acafd51
--- /dev/null
+++ b/examples/i18n.py
@@ -0,0 +1,82 @@
+"""
+Original docs link: https://docs.aiogram.dev/en/dev-3.x/utils/i18n.html
+PROBLEM SOLUTION PROVIDED:
+Aiogram handlers remember language on the start and there's no chance of changing it in handler's runtime.
+So, here's a little hack in `change_language handler`
+
+# Cheatsheet to create/update locales:
+## Generating new:
+1. `pybabel extract -k __ --input-dirs=. -o locales/messages.pot`
+2. `pybabel init -i locales/messages.pot -d locales -D messages -l <en ru uk>`
+3. Open `locales/{language}/LC_MESSAGES/messages.po` and Translate msgs
+4. `pybabel compile -d locales -D messages`
+
+## Updating:
+1. `pybabel extract -k __ --input-dirs=. -o locales/messages.pot`
+2. `pybabel update -d locales -D messages -i locales/messages.pot`
+3. Open `locales/{language}/LC_MESSAGES/messages.po` and Translate msgs
+4. `pybabel compile -d locales -D messages`
+
+"""
+import asyncio
+from typing import Any
+
+from aiogram import Bot, Dispatcher, Router
+from aiogram import types
+from aiogram.filters.command import Command, CommandStart
+from aiogram.utils.i18n import gettext as _, I18n
+from aiogram.utils.i18n.middleware import I18nMiddleware
+
+
+class BotI18nMiddleware(I18nMiddleware):
+    async def get_locale(self, event: types.Update | Any, data: dict[str, Any]) -> str:
+        # here is your logic, ex. get language from redis DB
+        return 'en'
+
+
+bot = Bot(token="<Your token>")
+router = Router()
+dp = Dispatcher()
+# NOTE: custom middleware is provided. You can use any middleware you want, ex: SimpleI18nMiddleware
+i18n_middleware = BotI18nMiddleware(
+    I18n(
+        path="locales",
+        default_locale="en",
+        domain="messages"
+    )
+)
+dp.update.outer_middleware(i18n_middleware)
+
+
+@router.message(CommandStart())
+async def start_handler(message: types.Message):
+    await message.answer(
+        _("Hello!. Write /language <new_lang>. Ex: /language ru")
+    )
+
+
+@router.message(Command("language"))
+async def change_language(message: types.Message):
+    """
+    This function dynamically changes language inside of handler
+    Handler input: /language <new_lang>. Ex: /language ru
+
+    Aiogram saves language context on start, so we should change language in runtime
+    """
+    new_lang = message.text.split(maxsplit=1)[1]
+    # change in runtime
+    with i18n_middleware.i18n.context(), i18n_middleware.i18n.use_locale(new_lang):
+        # all messages in this context will be translated to new_lang
+        await message.answer(_('Language was changed to {lang}').format(lang=new_lang))
+
+
+dp.include_router(router)
+
+
+async def main():
+    print("Bot started")
+    await dp.start_polling(bot)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

From c3fbe87ab417ed06dae4927a7cdc8972d94ddb15 Mon Sep 17 00:00:00 2001
From: Dmitry Buslov <buslovdmitrij0@gmail.com>
Date: Mon, 17 Mar 2025 00:02:30 +0200
Subject: [PATCH 2/3] Fix: rm custom i18n middleware so it doesn't confuse user

---
 examples/i18n.py | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/examples/i18n.py b/examples/i18n.py
index 6acafd51..89708d59 100644
--- a/examples/i18n.py
+++ b/examples/i18n.py
@@ -25,20 +25,20 @@ from aiogram import Bot, Dispatcher, Router
 from aiogram import types
 from aiogram.filters.command import Command, CommandStart
 from aiogram.utils.i18n import gettext as _, I18n
-from aiogram.utils.i18n.middleware import I18nMiddleware
+from aiogram.utils.i18n.middleware import I18nMiddleware, SimpleI18nMiddleware
 
 
-class BotI18nMiddleware(I18nMiddleware):
-    async def get_locale(self, event: types.Update | Any, data: dict[str, Any]) -> str:
-        # here is your logic, ex. get language from redis DB
-        return 'en'
+# class BotI18nMiddleware(I18nMiddleware):
+#     async def get_locale(self, event: types.Update | Any, data: dict[str, Any]) -> str:
+#         # here is your logic, ex. get language from redis DB.
+#         return 'en'
 
 
 bot = Bot(token="<Your token>")
 router = Router()
 dp = Dispatcher()
-# NOTE: custom middleware is provided. You can use any middleware you want, ex: SimpleI18nMiddleware
-i18n_middleware = BotI18nMiddleware(
+# NOTE: basic middleware is provided. You can customize your middleware, ex. BotI18nMiddleware
+i18n_middleware = SimpleI18nMiddleware(
     I18n(
         path="locales",
         default_locale="en",

From e3764961fb365d98778baad2db387dd972f5586e Mon Sep 17 00:00:00 2001
From: Dmitry Buslov <buslovdmitrij0@gmail.com>
Date: Mon, 17 Mar 2025 00:06:48 +0200
Subject: [PATCH 3/3] Feat: changelog

---
 CHANGES/1652.feature.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 CHANGES/1652.feature.rst

diff --git a/CHANGES/1652.feature.rst b/CHANGES/1652.feature.rst
new file mode 100644
index 00000000..81b15c9f
--- /dev/null
+++ b/CHANGES/1652.feature.rst
@@ -0,0 +1 @@
+Feature: Example of dynamic language switching in aiogram bot using i18n utilities, allowing real-time translation.