# -*- coding: utf-8 -*- r""" speaklater ~~~~~~~~~~ A module that provides lazy strings for translations. Basically you get an object that appears to be a string but changes the value every time the value is evaluated based on a callable you provide. For example you can have a global `lazy_gettext` function that returns a lazy string with the value of the current set language. Example: >>> from speaklater import make_lazy_string >>> sval = u'Hello World' >>> string = make_lazy_string(lambda: sval) This lazy string will evaluate to the value of the `sval` variable. >>> string lu'Hello World' >>> unicode(string) u'Hello World' >>> string.upper() u'HELLO WORLD' If you change the value, the lazy string will change as well: >>> sval = u'Hallo Welt' >>> string.upper() u'HALLO WELT' This is especially handy when combined with a thread local and gettext translations or dicts of translatable strings: >>> from speaklater import make_lazy_gettext >>> from threading import local >>> l = local() >>> l.translations = {u'Yes': 'Ja'} >>> lazy_gettext = make_lazy_gettext(lambda: l.translations.get) >>> yes = lazy_gettext(u'Yes') >>> print yes Ja >>> l.translations[u'Yes'] = u'Si' >>> print yes Si Lazy strings are no real strings so if you pass this sort of string to a function that performs an instance check, it will fail. In that case you have to explicitly convert it with `unicode` and/or `string` depending on what string type the lazy string encapsulates. To check if a string is lazy, you can use the `is_lazy_string` function: >>> from speaklater import is_lazy_string >>> is_lazy_string(u'yes') False >>> is_lazy_string(yes) True New in version 1.2: It's now also possible to pass keyword arguments to the callback used with `make_lazy_string`. :copyright: (c) 2010 by Armin Ronacher. :license: BSD, see LICENSE for more details. """ def is_lazy_string(obj): """Checks if the given object is a lazy string.""" return isinstance(obj, _LazyString) def make_lazy_string(__func, *args, **kwargs): """Creates a lazy string by invoking func with args.""" return _LazyString(__func, args, kwargs) def make_lazy_gettext(lookup_func): """Creates a lazy gettext function dispatches to a gettext function as returned by `lookup_func`. Example: >>> translations = {u'Yes': u'Ja'} >>> lazy_gettext = make_lazy_gettext(lambda: translations.get) >>> x = lazy_gettext(u'Yes') >>> x lu'Ja' >>> translations[u'Yes'] = u'Si' >>> x lu'Si' """ def lazy_gettext(string): if is_lazy_string(string): return string return make_lazy_string(lookup_func(), string) return lazy_gettext class _LazyString(object): """Class for strings created by a function call. The proxy implementation attempts to be as complete as possible, so that the lazy objects should mostly work as expected, for example for sorting. """ __slots__ = ('_func', '_args', '_kwargs') def __init__(self, func, args, kwargs): self._func = func self._args = args self._kwargs = kwargs value = property(lambda x: x._func(*x._args, **x._kwargs)) def __contains__(self, key): return key in self.value def __nonzero__(self): return bool(self.value) def __dir__(self): return dir(unicode) def __iter__(self): return iter(self.value) def __len__(self): return len(self.value) def __str__(self): return str(self.value) def __unicode__(self): return unicode(self.value) def __add__(self, other): return self.value + other def __radd__(self, other): return other + self.value def __mod__(self, other): return self.value % other def __rmod__(self, other): return other % self.value def __mul__(self, other): return self.value * other def __rmul__(self, other): return other * self.value def __lt__(self, other): return self.value < other def __le__(self, other): return self.value <= other def __eq__(self, other): return self.value == other def __ne__(self, other): return self.value != other def __gt__(self, other): return self.value > other def __ge__(self, other): return self.value >= other def __getattr__(self, name): if name == '__members__': return self.__dir__() return getattr(self.value, name) def __getstate__(self): return self._func, self._args, self._kwargs def __setstate__(self, tup): self._func, self._args, self._kwargs = tup def __getitem__(self, key): return self.value[key] def __copy__(self): return self def __repr__(self): try: return 'l' + repr(self.value) except Exception: return '<%s broken>' % self.__class__.__name__ if __name__ == '__main__': import doctest doctest.testmod()