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# -*- 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, text_type
>>> sval = u'Hello World'
>>> string = make_lazy_string(lambda: sval)
This lazy string will evaluate to the value of the `sval` variable.
>>> string
l'Hello World'
>>> text_type(string) == u'Hello World'
True
>>> string.upper() == u'HELLO WORLD'
True
If you change the value, the lazy string will change as well:
>>> sval = u'Hallo Welt'
>>> string.upper() == u'HALLO WELT'
True
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 1.4: python >= 3.3 (and also 2.6 and 2.7) support,
repr(lazystring) is l"foo" on py2 and py3 - no "u" on py2!
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.
"""
import sys
PY2 = sys.version_info[0] == 2
_identity = lambda x: x
if not PY2:
text_type = str
implements_to_string = _identity
implements_bool = _identity
else:
text_type = unicode
def implements_to_string(cls):
cls.__unicode__ = cls.__str__
cls.__str__ = lambda x: x.__unicode__().encode('utf-8')
return cls
def implements_bool(cls):
cls.__nonzero__ = cls.__bool__
del cls.__bool__
return cls
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
l'Ja'
>>> translations[u'Yes'] = u'Si'
>>> x
l'Si'
"""
def lazy_gettext(string):
if is_lazy_string(string):
return string
return make_lazy_string(lookup_func(), string)
return lazy_gettext
@implements_bool
@implements_to_string
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 __bool__(self):
return bool(self.value)
def __dir__(self):
return dir(text_type)
def __iter__(self):
return iter(self.value)
def __len__(self):
return len(self.value)
def __str__(self):
return text_type(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:
r = repr(self.value)
if PY2 and r.startswith('u'):
r = r[1:] # make it look same as on py3
return 'l' + r
except Exception:
return '<%s broken>' % self.__class__.__name__
if __name__ == '__main__':
import doctest
doctest.testmod()