Babel

安装依赖

uv add Babel
# pip install Babel

语言

提取源字符串

定义 babel.cfg 配置

[python: **.py]
encoding = utf-8

定义函数

• cast用于覆盖函数定义消除IDE警告
• 注释 # Translator: 用于生成 .pot 文件时带入注释，可自定义

from typing import Callable, cast

import gettext
import os

LOCALES_DIR = os.path.join(os.path.dirname(__file__), 'translations')


def get_translator(lang):
    # 如果找不到语言，回退到默认 gettext.NullTranslations()
    try:
        t = gettext.translation('messages', localedir=LOCALES_DIR, languages=[lang])
    except FileNotFoundError:
        t = gettext.NullTranslations()
    _gettext = cast(Callable[[str], str], t.gettext)
    _ngettext = cast(Callable[[str, str, int], str], t.ngettext)
    return _gettext, _ngettext


def show_messages(lang, counts=(0, 1, 2, 5)):
    _, ngettext = get_translator(lang)
    print(f'--- language: {lang} ---')
    # 简单消息
    print(_('Hello, world!'))
    # 带占位符
    for n in counts:
        # Translator: 使用 ngettext 处理单复数
        msg = ngettext('There is %(num)d apple', 'There are %(num)d apples', n) % {'num': n}
        print(msg)
    print()


if __name__ == '__main__':
    print()
    # 演示英文和中文
    show_messages('en')
    show_messages('zh_CN')

提取源字符串命令

uv run pybabel extract --add-comments=Translator -F babel.cfg -o messages.pot .

初始化新语言

uv run pybabel init -l zh_CN -d locales -i messages.pot
uv run pybabel init -l en_US -d locales -i messages.pot

更新现有翻译

uv run pybabel update -d locales -i messages.pot

po文件编译成mo

uv run pybabel compile -d locales

数字/货币

from babel.numbers import (
    format_decimal, parse_decimal,
    format_percent,
    format_currency,
    NumberFormatError,
)

print()
# 小数
print(format_decimal(12345.678, locale="zh_CN")) # 12,345.678
print(format_decimal(12345.678, locale="en_US")) # 12,345.678
print(format_decimal(12345.678, locale="sv_SE")) # 12 345,678
print(format_decimal(12345.678, locale="de_DE")) # 12.345,678
try:
    print(parse_decimal('1,099.98', locale='en_US')) # 1099.98
    print(parse_decimal('1.099,98', locale='de')) # 1099.98
    print(parse_decimal('2,109,998', locale='de')) # raise NumberFormatError
except NumberFormatError as ex:
    print(ex)

# 百分比
print(format_percent(0.2567, locale="zh_CN"))  # 25.67%
print(format_percent(0.2567, locale="en_US"))  # 25.67%
print(format_percent(25.1234, locale='sv_SE'))  # 25.67%

# 货币
print(format_currency(12345.67, 'CNY', locale='zh_CN'))  # ￥12,345.67
print(format_currency(12345.67, 'USD', locale='en_US'))  # $12,345.67

日期、时间

from babel.dates import format_datetime
from datetime import datetime
from zoneinfo import ZoneInfo

print()
# 数据库时间（+8 时区，北京时间）
db_time = datetime(
    2025, 11, 8, 21, 0, 0,
    tzinfo=ZoneInfo("Asia/Shanghai")
)
# 假设用户在美国东部（UTC-5）
tz_ny = ZoneInfo("America/New_York")

# 转换到用户时区
user_time = db_time.astimezone(tz_ny)

# 格式化显示
print(format_datetime(user_time, locale="en_US"))  # 美国用户看到本地时间
print(format_datetime(db_time, locale="zh_CN"))  # 中国用户看到北京时间

夏令时

from datetime import datetime
from zoneinfo import ZoneInfo

print()
tz_NY = ZoneInfo("America/New_York")
dt_NY = datetime(2024, 7, 15, 12, 0, 0, tzinfo=tz_NY)
print(f"夏令时间：{dt_NY}") # 2024-07-15 12:00:00-04:00
dt_NY = datetime(2024, 1, 15, 12, 0, 0, tzinfo=tz_NY)
print(f"冬令时间：{dt_NY}") # 2024-01-15 12:00:00-05:00