Python django.utils.functional 模块，Promise() 实例源码

def default(self, o,
                dates=(datetime.datetime, datetime.date),
                times=(datetime.time,),
                textual=(decimal.Decimal, uuid.UUID, DjangoPromise),
                isinstance=isinstance,
                datetime=datetime.datetime,
                text_type=text_type):
        if isinstance(o, dates):
            if not isinstance(o, datetime):
                o = datetime(o.year, o.month, o.day, 0, 0, 0, 0)
            r = o.isoformat()
            if r.endswith("+00:00"):
                r = r[:-6] + "Z"
            return r
        elif isinstance(o, times):
            return o.isoformat()
        elif isinstance(o, textual):
            return text_type(o)
        else:
            return super(JsonEncoder, self).default(o)

def smart_repr(value):
    if isinstance(value, models.Manager):
        return manager_repr(value)

    if isinstance(value, Promise) and value._delegate_text:
        value = force_text(value)

    value = unicode_repr(value)

    # Representations like u'help text'
    # should simply be presented as 'help text'
    if value.startswith("u'") and value.endswith("'"):
        return value[1:]

    # Representations like
    # <django.core.validators.RegexValidator object at 0x1047af050>
    # Should be presented as
    # <django.core.validators.RegexValidator object>
    value = re.sub(' at 0x[0-9A-Fa-f]{4,32}>', '>', value)

    return value

def smart_repr(value):
    if isinstance(value, models.Manager):
        return manager_repr(value)

    if isinstance(value, Promise) and value._delegate_text:
        value = force_text(value)

    value = unicode_repr(value)

    # Representations like u'help text'
    # should simply be presented as 'help text'
    if value.startswith("u'") and value.endswith("'"):
        return value[1:]

    # Representations like
    # <django.core.validators.RegexValidator object at 0x1047af050>
    # Should be presented as
    # <django.core.validators.RegexValidator object>
    value = re.sub(' at 0x[0-9A-Fa-f]{4,32}>', '>', value)

    return value

def mark_safe(s):
    """
    Explicitly mark a string as safe for (HTML) output purposes. The returned
    object can be used everywhere a string or unicode object is appropriate.

    If used on a method as a decorator, mark the returned data as safe.

    Can be called multiple times on a single string.
    """
    if hasattr(s, '__html__'):
        return s
    if isinstance(s, bytes) or (isinstance(s, Promise) and s._delegate_bytes):
        return SafeBytes(s)
    if isinstance(s, (six.text_type, Promise)):
        return SafeText(s)
    if callable(s):
        return _safety_decorator(mark_safe, s)
    return SafeString(str(s))

def mark_for_escaping(s):
    """
    Explicitly mark a string as requiring HTML escaping upon output. Has no
    effect on SafeData subclasses.

    Can be called multiple times on a single string (the resulting escaping is
    only applied once).
    """
    warnings.warn('mark_for_escaping() is deprecated.', RemovedInDjango20Warning)
    if hasattr(s, '__html__') or isinstance(s, EscapeData):
        return s
    if isinstance(s, bytes) or (isinstance(s, Promise) and s._delegate_bytes):
        return EscapeBytes(s)
    if isinstance(s, (six.text_type, Promise)):
        return EscapeText(s)
    return EscapeString(str(s))

def mark_safe(s):
    """
    Explicitly mark a string as safe for (HTML) output purposes. The returned
    object can be used everywhere a string or unicode object is appropriate.

    If used on a method as a decorator, mark the returned data as safe.

    Can be called multiple times on a single string.
    """
    if hasattr(s, '__html__'):
        return s
    if isinstance(s, bytes) or (isinstance(s, Promise) and s._delegate_bytes):
        return SafeBytes(s)
    if isinstance(s, (six.text_type, Promise)):
        return SafeText(s)
    if callable(s):
        return _safety_decorator(mark_safe, s)
    return SafeString(str(s))

def mark_for_escaping(s):
    """
    Explicitly mark a string as requiring HTML escaping upon output. Has no
    effect on SafeData subclasses.

    Can be called multiple times on a single string (the resulting escaping is
    only applied once).
    """
    warnings.warn('mark_for_escaping() is deprecated.', RemovedInDjango20Warning)
    if hasattr(s, '__html__') or isinstance(s, EscapeData):
        return s
    if isinstance(s, bytes) or (isinstance(s, Promise) and s._delegate_bytes):
        return EscapeBytes(s)
    if isinstance(s, (six.text_type, Promise)):
        return EscapeText(s)
    return EscapeString(str(s))

def default(self, obj):
        if isinstance(obj, Promise):
            return force_text(obj)
        return super(LazyTranslationEncoder, self).default(obj)

def resolve_url(to, *args, **kwargs):
    """
    Return a URL appropriate for the arguments passed.

    The arguments could be:

        * A model: the model's `get_absolute_url()` function will be called.

        * A view name, possibly with arguments: `urlresolvers.reverse()` will
          be used to reverse-resolve the name.

        * A URL, which will be returned as-is.
    """
    # If it's a model, use get_absolute_url()
    if hasattr(to, 'get_absolute_url'):
        return to.get_absolute_url()

    if isinstance(to, Promise):
        # Expand the lazy instance, as it can cause issues when it is passed
        # further to some Python functions like urlparse.
        to = force_text(to)

    if isinstance(to, six.string_types):
        # Handle relative URLs
        if to.startswith(('./', '../')):
            return to

    # Next try a reverse URL resolution.
    try:
        return urlresolvers.reverse(to, args=args, kwargs=kwargs)
    except urlresolvers.NoReverseMatch:
        # If this is a callable, re-raise.
        if callable(to):
            raise
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise

    # Finally, fall back and assume it's a URL
    return to

def get_prep_value(self, value):
        """
        Perform preliminary non-db specific value checks and conversions.
        """
        if isinstance(value, Promise):
            value = value._proxy____cast()
        return value

def smart_text(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a text object representing 's' -- unicode on Python 2 and str on
    Python 3. Treats bytestrings using the 'encoding' codec.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_text(s, encoding, strings_only, errors)

def smart_bytes(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a bytestring version of 's', encoded as specified in 'encoding'.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_bytes(s, encoding, strings_only, errors)

def force_bytes(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Similar to smart_bytes, except that lazy instances are resolved to
    strings, rather than kept as lazy objects.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    # Handle the common case first for performance reasons.
    if isinstance(s, bytes):
        if encoding == 'utf-8':
            return s
        else:
            return s.decode('utf-8', errors).encode(encoding, errors)
    if strings_only and is_protected_type(s):
        return s
    if isinstance(s, six.memoryview):
        return bytes(s)
    if isinstance(s, Promise):
        return six.text_type(s).encode(encoding, errors)
    if not isinstance(s, six.string_types):
        try:
            if six.PY3:
                return six.text_type(s).encode(encoding)
            else:
                return bytes(s)
        except UnicodeEncodeError:
            if isinstance(s, Exception):
                # An Exception subclass containing non-ASCII data that doesn't
                # know how to print itself properly. We shouldn't raise a
                # further exception.
                return b' '.join(force_bytes(arg, encoding, strings_only, errors)
                                 for arg in s)
            return six.text_type(s).encode(encoding, errors)
    else:
        return s.encode(encoding, errors)

def mark_for_escaping(s):
    """
    Explicitly mark a string as requiring HTML escaping upon output. Has no
    effect on SafeData subclasses.

    Can be called multiple times on a single string (the resulting escaping is
    only applied once).
    """
    if hasattr(s, '__html__') or isinstance(s, EscapeData):
        return s
    if isinstance(s, bytes) or (isinstance(s, Promise) and s._delegate_bytes):
        return EscapeBytes(s)
    if isinstance(s, (six.text_type, Promise)):
        return EscapeText(s)
    return EscapeString(str(s))

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

# Older, deprecated class name (for backwards compatibility purposes).

def obj_as_dict(o):

    if isinstance(o, DeclarativeFieldsMetaclass):
        o = FormSerializer(form=o).data

    if isinstance(o, forms.Field):
        o = FormFieldSerializer(field=o).data

    if isinstance(o, forms.Widget):
        o = FormWidgetSerializer(widget=o).data

    if isinstance(o, (list, tuple)):
        o = [obj_as_dict(x) for x in o]

    if isinstance(o, Promise):
        try:
            o = force_unicode(o)
        except:
            # Item could be a lazy tuple or list
            try:
                o = [obj_as_dict(x) for x in o]
            except:
                raise Exception('Unable to resolve lazy object %s' % o)
    if callable(o):
        o = o()

    if isinstance(o, dict):
        for k, v in o.items():
            o[k] = obj_as_dict(v)

    return o

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, datetime.timedelta):
            return duration_iso_string(o)
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        elif isinstance(o, CallableBool):
            return bool(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

def default(self, o):
        if isinstance(o, datetime.datetime):
            return o.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(o, datetime.date):
            return o.strftime('%Y-%m-%d')
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, Promise):
            return force_text(o)
        else:
            try:
                return super(JSONEncoder, self).default(o)
            except Exception:
                return smart_text(o)

def default(self, o):
        if isinstance(o, datetime.datetime):
            return o.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(o, datetime.date):
            return o.strftime('%Y-%m-%d')
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, Promise):
            return force_text(o)
        else:
            try:
                return super(JSONEncoder, self).default(o)
            except Exception:
                return smart_text(o)

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, datetime.timedelta):
            return duration_iso_string(o)
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        elif isinstance(o, CallableBool):
            return bool(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

def default(self, o):
        if isinstance(o, datetime.datetime):
            return o.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(o, datetime.date):
            return o.strftime('%Y-%m-%d')
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, Promise):
            return force_text(o)
        else:
            try:
                return super(JSONEncoder, self).default(o)
            except Exception:
                return smart_text(o)

def default(self, obj):
        if isinstance(obj, Promise):
            return force_text(obj)
        return super(LazyEncoder, self).default(obj)

def default(self, obj):
        if isinstance(obj, Promise):
            return force_text(obj)
        return super().default(obj)

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

# Older, deprecated class name (for backwards compatibility purposes).

def resolve_url(to, *args, **kwargs):
    """
    Return a URL appropriate for the arguments passed.

    The arguments could be:

        * A model: the model's `get_absolute_url()` function will be called.

        * A view name, possibly with arguments: `urlresolvers.reverse()` will
          be used to reverse-resolve the name.

        * A URL, which will be returned as-is.

    """
    # If it's a model, use get_absolute_url()
    if hasattr(to, 'get_absolute_url'):
        return to.get_absolute_url()

    if isinstance(to, Promise):
        # Expand the lazy instance, as it can cause issues when it is passed
        # further to some Python functions like urlparse.
        to = force_text(to)

    if isinstance(to, six.string_types):
        # Handle relative URLs
        if any(to.startswith(path) for path in ('./', '../')):
            return to

    # Next try a reverse URL resolution.
    try:
        return urlresolvers.reverse(to, args=args, kwargs=kwargs)
    except urlresolvers.NoReverseMatch:
        # If this is a callable, re-raise.
        if callable(to):
            raise
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise

    # Finally, fall back and assume it's a URL
    return to

def default(self, obj):
        if isinstance(obj, Promise):
            return force_unicode(obj)
        return super(LazyEncoder, self).default(obj)

def smart_text(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a text object representing 's' -- unicode on Python 2 and str on
    Python 3. Treats bytestrings using the 'encoding' codec.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_text(s, encoding, strings_only, errors)

def smart_bytes(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a bytestring version of 's', encoded as specified in 'encoding'.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_bytes(s, encoding, strings_only, errors)

def force_bytes(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Similar to smart_bytes, except that lazy instances are resolved to
    strings, rather than kept as lazy objects.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, six.memoryview):
        s = bytes(s)
    if isinstance(s, bytes):
        if encoding == 'utf-8':
            return s
        else:
            return s.decode('utf-8', errors).encode(encoding, errors)
    if strings_only and (s is None or isinstance(s, int)):
        return s
    if isinstance(s, Promise):
        return six.text_type(s).encode(encoding, errors)
    if not isinstance(s, six.string_types):
        try:
            if six.PY3:
                return six.text_type(s).encode(encoding)
            else:
                return bytes(s)
        except UnicodeEncodeError:
            if isinstance(s, Exception):
                # An Exception subclass containing non-ASCII data that doesn't
                # know how to print itself properly. We shouldn't raise a
                # further exception.
                return b' '.join([force_bytes(arg, encoding, strings_only,
                        errors) for arg in s])
            return six.text_type(s).encode(encoding, errors)
    else:
        return s.encode(encoding, errors)

def default(self, obj):
        # For Date Time string spec, see ECMA 262
        # http://ecma-international.org/ecma-262/5.1/#sec-15.9.1.15
        if isinstance(obj, Promise):
            return force_text(obj)
        elif isinstance(obj, datetime.datetime):
            representation = obj.isoformat()
            if obj.microsecond:
                representation = representation[:23] + representation[26:]
            if representation.endswith('+00:00'):
                representation = representation[:-6] + 'Z'
            return representation
        elif isinstance(obj, datetime.date):
            return obj.isoformat()
        elif isinstance(obj, datetime.time):
            if timezone and timezone.is_aware(obj):
                raise ValueError("JSON can't represent timezone-aware times.")
            representation = obj.isoformat()
            if obj.microsecond:
                representation = representation[:12]
            return representation
        elif isinstance(obj, datetime.timedelta):
            return six.text_type(total_seconds(obj))
        elif isinstance(obj, decimal.Decimal):
            # Serializers will coerce decimals to strings by default.
            return float(obj)
        elif isinstance(obj, uuid.UUID):
            return six.text_type(obj)
        elif isinstance(obj, QuerySet):
            return tuple(obj)
        elif hasattr(obj, 'tolist'):
            # Numpy arrays and array scalars.
            return obj.tolist()
        elif hasattr(obj, '__getitem__'):
            try:
                return dict(obj)
            except:
                pass
        elif hasattr(obj, '__iter__'):
            return tuple(item for item in obj)
        return super(JSONEncoder, self).default(obj)

def resolve_url(to, *args, **kwargs):
    """
    Return a URL appropriate for the arguments passed.

    The arguments could be:

        * A model: the model's `get_absolute_url()` function will be called.

        * A view name, possibly with arguments: `urlresolvers.reverse()` will
          be used to reverse-resolve the name.

        * A URL, which will be returned as-is.

    """
    # If it's a model, use get_absolute_url()
    if hasattr(to, 'get_absolute_url'):
        return to.get_absolute_url()

    if isinstance(to, Promise):
        # Expand the lazy instance, as it can cause issues when it is passed
        # further to some Python functions like urlparse.
        to = force_text(to)

    if isinstance(to, six.string_types):
        # Handle relative URLs
        if any(to.startswith(path) for path in ('./', '../')):
            return to

    # Next try a reverse URL resolution.
    try:
        return urlresolvers.reverse(to, args=args, kwargs=kwargs)
    except urlresolvers.NoReverseMatch:
        # If this is a callable, re-raise.
        if callable(to):
            raise
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise

    # Finally, fall back and assume it's a URL
    return to

def resolve_url(to, *args, **kwargs):
    """
    Return a URL appropriate for the arguments passed.

    The arguments could be:

        * A model: the model's `get_absolute_url()` function will be called.

        * A view name, possibly with arguments: `urlresolvers.reverse()` will
          be used to reverse-resolve the name.

        * A URL, which will be returned as-is.

    """
    # If it's a model, use get_absolute_url()
    if hasattr(to, 'get_absolute_url'):
        return to.get_absolute_url()

    if isinstance(to, Promise):
        # Expand the lazy instance, as it can cause issues when it is passed
        # further to some Python functions like urlparse.
        to = force_text(to)

    if isinstance(to, six.string_types):
        # Handle relative URLs
        if any(to.startswith(path) for path in ('./', '../')):
            return to

    # Next try a reverse URL resolution.
    try:
        return urlresolvers.reverse(to, args=args, kwargs=kwargs)
    except urlresolvers.NoReverseMatch:
        # If this is a callable, re-raise.
        if callable(to):
            raise
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise

    # Finally, fall back and assume it's a URL
    return to

def is_non_str_iterable(obj):
        # noinspection PyProtectedMember
        if isinstance(obj, str) or (isinstance(obj, Promise) and obj._delegate_text):
            return False
        return hasattr(obj, '__iter__')

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

# Older, deprecated class name (for backwards compatibility purposes).

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, datetime.timedelta):
            return duration_iso_string(o)
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

def resolve_url(to, *args, **kwargs):
    """
    Return a URL appropriate for the arguments passed.

    The arguments could be:

        * A model: the model's `get_absolute_url()` function will be called.

        * A view name, possibly with arguments: `urls.reverse()` will be used
          to reverse-resolve the name.

        * A URL, which will be returned as-is.
    """
    # If it's a model, use get_absolute_url()
    if hasattr(to, 'get_absolute_url'):
        return to.get_absolute_url()

    if isinstance(to, Promise):
        # Expand the lazy instance, as it can cause issues when it is passed
        # further to some Python functions like urlparse.
        to = force_text(to)

    if isinstance(to, six.string_types):
        # Handle relative URLs
        if to.startswith(('./', '../')):
            return to

    # Next try a reverse URL resolution.
    try:
        return reverse(to, args=args, kwargs=kwargs)
    except NoReverseMatch:
        # If this is a callable, re-raise.
        if callable(to):
            raise
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise

    # Finally, fall back and assume it's a URL
    return to

def get_prep_value(self, value):
        """
        Perform preliminary non-db specific value checks and conversions.
        """
        if isinstance(value, Promise):
            value = value._proxy____cast()
        return value

def smart_text(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a text object representing 's' -- unicode on Python 2 and str on
    Python 3. Treats bytestrings using the 'encoding' codec.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_text(s, encoding, strings_only, errors)

def smart_bytes(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a bytestring version of 's', encoded as specified in 'encoding'.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_bytes(s, encoding, strings_only, errors)

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

# Older, deprecated class name (for backwards compatibility purposes).

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

# Older, deprecated class name (for backwards compatibility purposes).

def may_be_lazy(thing):
    if isinstance(thing, Promise):
        return thing._proxy____args[0]
    else:
        return thing

def default(self, o):
        if isinstance(o, Promise):
            return force_text(o)
        return super(SafeJSONEncoder, self).default(o)

def default(self, o):
        # See "Date Time String Format" in the ECMA-262 specification.
        if isinstance(o, datetime.datetime):
            r = o.isoformat()
            if o.microsecond:
                r = r[:23] + r[26:]
            if r.endswith('+00:00'):
                r = r[:-6] + 'Z'
            return r
        elif isinstance(o, datetime.date):
            return o.isoformat()
        elif isinstance(o, datetime.time):
            if is_aware(o):
                raise ValueError("JSON can't represent timezone-aware times.")
            r = o.isoformat()
            if o.microsecond:
                r = r[:12]
            return r
        elif isinstance(o, datetime.timedelta):
            return duration_iso_string(o)
        elif isinstance(o, decimal.Decimal):
            return str(o)
        elif isinstance(o, uuid.UUID):
            return str(o)
        elif isinstance(o, Promise):
            return six.text_type(o)
        else:
            return super(DjangoJSONEncoder, self).default(o)

def resolve_url(to, *args, **kwargs):
    """
    Return a URL appropriate for the arguments passed.

    The arguments could be:

        * A model: the model's `get_absolute_url()` function will be called.

        * A view name, possibly with arguments: `urls.reverse()` will be used
          to reverse-resolve the name.

        * A URL, which will be returned as-is.
    """
    # If it's a model, use get_absolute_url()
    if hasattr(to, 'get_absolute_url'):
        return to.get_absolute_url()

    if isinstance(to, Promise):
        # Expand the lazy instance, as it can cause issues when it is passed
        # further to some Python functions like urlparse.
        to = force_text(to)

    if isinstance(to, six.string_types):
        # Handle relative URLs
        if to.startswith(('./', '../')):
            return to

    # Next try a reverse URL resolution.
    try:
        return reverse(to, args=args, kwargs=kwargs)
    except NoReverseMatch:
        # If this is a callable, re-raise.
        if callable(to):
            raise
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise

    # Finally, fall back and assume it's a URL
    return to

def get_prep_value(self, value):
        """
        Perform preliminary non-db specific value checks and conversions.
        """
        if isinstance(value, Promise):
            value = value._proxy____cast()
        return value

def smart_text(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a text object representing 's' -- unicode on Python 2 and str on
    Python 3. Treats bytestrings using the 'encoding' codec.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_text(s, encoding, strings_only, errors)

def smart_bytes(s, encoding='utf-8', strings_only=False, errors='strict'):
    """
    Returns a bytestring version of 's', encoded as specified in 'encoding'.

    If strings_only is True, don't convert (some) non-string-like objects.
    """
    if isinstance(s, Promise):
        # The input is the result of a gettext_lazy() call.
        return s
    return force_bytes(s, encoding, strings_only, errors)

def resolve_url(to, *args, **kwargs):
    """
    Return a URL appropriate for the arguments passed.

    The arguments could be:

        * A model: the model's `get_absolute_url()` function will be called.

        * A view name, possibly with arguments: `urlresolvers.reverse()` will
          be used to reverse-resolve the name.

        * A URL, which will be returned as-is.
    """
    # If it's a model, use get_absolute_url()
    if hasattr(to, 'get_absolute_url'):
        return to.get_absolute_url()

    if isinstance(to, Promise):
        # Expand the lazy instance, as it can cause issues when it is passed
        # further to some Python functions like urlparse.
        to = force_text(to)

    if isinstance(to, six.string_types):
        # Handle relative URLs
        if to.startswith(('./', '../')):
            return to

    # Next try a reverse URL resolution.
    try:
        return urlresolvers.reverse(to, args=args, kwargs=kwargs)
    except urlresolvers.NoReverseMatch:
        # If this is a callable, re-raise.
        if callable(to):
            raise
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise

    # Finally, fall back and assume it's a URL
    return to

def get_prep_value(self, value):
        """
        Perform preliminary non-db specific value checks and conversions.
        """
        if isinstance(value, Promise):
            value = value._proxy____cast()
        return value