translatable_urls.py

import functools
from flask import Flask, g

app = Flask(__name__)
languages = ['en', 'hr']

def translate_to(lang, text):
    return {
        '/about': {
            'hr': '/onama',
        },
        "Hello, World": {
            'hr': "Bok svijete",
        }
    }[text].get(lang, text)


def int_route(path):
    def decorator(f):
        @functools.wraps(f)
        def decorated(lang, *args, **kwargs):
            g.lang = lang
            return f(*args, **kwargs)

        for lang in languages:
            app.route('/' + lang + translate_to(lang, path), defaults={'lang': lang})(decorated)

        return decorated
    return decorator



@int_route('/about')
def about():
    return translate_to(g.lang, "Hello, World")


if __name__ == '__main__':
    app.run(debug=True)