Babel: Internationalization Utilities for Python

2.18.0 verified Tue May 12 auth: no python install: verified quickstart: verified

Babel is a collection of tools for internationalizing Python applications, with an emphasis on web-based applications. The current version is 2.18.0, released on February 26, 2026. Babel follows an annual release cadence, with major updates typically occurring once a year.

pip install babel

Common errors

error ModuleNotFoundError: No module named 'babel' ↓

cause This error occurs when the 'babel' package is not installed in the Python environment being used, or there's a mismatch between the Python interpreter running the code and where Babel was installed.

fix

Install the Babel library using pip: pip install Babel. If using virtual environments, ensure the correct environment is activated. If multiple Python versions are present, use python -m pip install Babel to ensure installation into the target interpreter.

error AttributeError: 'Babel' object has no attribute 'localeselector' ↓

cause This error typically arises when using Flask-Babel, indicating an incompatibility or incorrect usage of the `localeselector` decorator due to API changes in Flask-Babel v3.0.0 or newer.

fix

Instead of using the @babel.localeselector decorator, pass the locale selector function directly to the Babel constructor or the init_app method, for example: babel = Babel(app, locale_selector=get_locale) or babel.init_app(app, locale_selector=get_locale).

error pybabel: error: no input files or directories specified ↓

cause This error occurs when the `pybabel extract` command is run without specifying the source files or directories from which to extract translatable messages.

fix

Provide the input directory using the --input-dirs option or by adding a dot . to represent the current directory, for example: pybabel extract -F babel.cfg -o messages.pot --input-dirs=..

error RuntimeError: The babel data files are not available. ↓

cause This error indicates that Babel's Common Locale Data Repository (CLDR) files, which contain locale-specific data, are missing. This often happens after a source installation or when certain package managers don't include them.

fix

If installing from source, ensure you run python setup.py import_cldr before python setup.py install. If installed via a package manager, ensure the babel package (or python-babel on some systems) is correctly installed and its data dependencies are met.

error ModuleNotFoundError: No module named 'babel.numbers' ↓

cause This specific ModuleNotFoundError typically occurs when a submodule like `babel.numbers` is used without an explicit import, or when tools like Pyinstaller fail to detect such nested imports during packaging.

fix

Explicitly import the submodule where it's needed, for instance: from babel.numbers import format_decimal. If using Pyinstaller, add --hidden-import babel.numbers to your Pyinstaller command or .spec file.

Warnings

breaking Babel 2.15.0 dropped support for Python 3.7, requiring Python 3.8 or newer. ↓

fix Upgrade to Python 3.8 or later to maintain compatibility.

deprecated The 'format_datetime' function is deprecated and will be removed in a future release. ↓

fix Use 'format_date' or 'format_time' as appropriate for your use case.

Install compatibility verified last tested: 2026-05-12

python os / libc status wheel install import disk

3.10 alpine (musl) - - 0.04s 50.7M

3.10 slim (glibc) - - 0.03s 51M

3.11 alpine (musl) - - 0.07s 52.7M

3.11 slim (glibc) - - 0.05s 53M

3.12 alpine (musl) - - 0.05s 44.5M

3.12 slim (glibc) - - 0.05s 45M

3.13 alpine (musl) - - 0.04s 44.1M

3.13 slim (glibc) - - 0.04s 45M

3.9 alpine (musl) - - 0.04s 50.2M

3.9 slim (glibc) - - 0.03s 51M

Imports

format_date
```
from babel.dates import format_date
```
Ensure correct import path to access date formatting functions

Quickstart verified last tested: 2026-04-23

This example demonstrates how to set a locale and format a date accordingly using Babel.

from babel import Locale

# Set the locale to French
locale = Locale('fr', 'FR')

# Format a date in the French locale
from babel.dates import format_date
from datetime import datetime

date = datetime(2026, 3, 28)
formatted_date = format_date(date, locale=locale)
print(formatted_date)  # Output: 28 mars 2026