An implementation of lazy strings. Can be used in combination with gettext for the translation of web apps.

It's less beautiful than speaklater (an other implementation of lazy strings), but I wanted lazy strings that work even if a single thread interleaves the processing of many http requests (this happens with async frameworks).

postpone doesn't rely on a global state. And it doesn't use the thread.local() trick that speaklater uses either.

Example of use:

>>> from postpone import evalr, LazyString as _

>>> translations = {
        "Order {item}.": "Commander {item}.",
        "Take a nap": "Faire une sieste",
        "Stare at the wall for %s minutes.": "Fixer le mur pendant %s minutes." ,
        "a new pillow": "un nouvel oreiller"
    }

>>> tasklist = [
        _("Order {item}.").format(item = _("a new pillow")),
        _("Take a nap") + '!',
        _("Stare at the wall for %s minutes.") % 30
    ]

>>> evalr(tasklist, translations.get)
['Commander un nouvel oreiller.', 'Faire une sieste!', 'Fixer le mur pendant 30 minutes.']

evalr walks python dictionaries, lists, tuples or sets and apply a function to all the strings wrapped inside a LazyString object.

To apply a function to the strings inside a single expression, you can use the eval method:

>>> s = _("Take a nap") + '!'

>>> s.eval(str.upper)
'TAKE A NAP!'

>>> s.eval(translations.get)
'Faire une sieste!'

Or, again, the evalr function

>>> evalr(_("a new pillow").capitalize(), translations.get)
'Un nouvel oreiller'

For most projects containing more than a few strings or languages, you'll probably want to use the gettext module to supply you with a translation function.

import gettext
translation = gettext.translation("myproject", "./locale", ["fr"])
translated_tasklist = evalr(tasklist, translation.ugettext)

GitHub repo: https://github.com/leforestier/postpone