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