class FilterExpression

from django.template.base import FilterExpression 
Parse a variable token and its optional filters (all as a single string),
and return a list of tuples of the filter name and arguments.
Sample::

    >>> token = 'variable|default:"Default value"|date:"Y-m-d"'
    >>> p = Parser('')
    >>> fe = FilterExpression(token, p)
    >>> len(fe.filters)
    2
    >>> fe.var
    <Variable: 'variable'>

Ancestors (MRO)

  1. builtins.object
  2. django.template.base.FilterExpression

Fields

AttributeTypeDefined in

Methods

def __init__(self, token, parser)
django.template.base.FilterExpression 
Initialize self.  See help(type(self)) for accurate signature.
    def __init__(self, token, parser):
        self.token = token
        matches = filter_re.finditer(token)
        var_obj = None
        filters = []
        upto = 0
        for match in matches:
            start = match.start()
            if upto != start:
                raise TemplateSyntaxError(
                    "Could not parse some characters: "
                    "%s|%s|%s" % (token[:upto], token[upto:start], token[start:])
                )
            if var_obj is None:
                if constant := match["constant"]:
                    try:
                        var_obj = Variable(constant).resolve({})
                    except VariableDoesNotExist:
                        var_obj = None
                elif (var := match["var"]) is None:
                    raise TemplateSyntaxError(
                        "Could not find variable at start of %s." % token
                    )
                else:
                    var_obj = Variable(var)
            else:
                filter_name = match["filter_name"]
                args = []
                if constant_arg := match["constant_arg"]:
                    args.append((False, Variable(constant_arg).resolve({})))
                elif var_arg := match["var_arg"]:
                    args.append((True, Variable(var_arg)))
                filter_func = parser.find_filter(filter_name)
                self.args_check(filter_name, filter_func, args)
                filters.append((filter_func, args))
            upto = match.end()
        if upto != len(token):
            raise TemplateSyntaxError(
                "Could not parse the remainder: '%s' "
                "from '%s'" % (token[upto:], token)
            )

        self.filters = filters
        self.var = var_obj
        self.is_var = isinstance(var_obj, Variable)

def __repr__(self)
django.template.base.FilterExpression 
Return repr(self).
    def __repr__(self):
        return "<%s %r>" % (self.__class__.__qualname__, self.token)

def __str__(self)
django.template.base.FilterExpression 
Return str(self).
    def __str__(self):
        return self.token

def args_check(name, func, provided)
django.template.base.FilterExpression 
    def args_check(name, func, provided):
        provided = list(provided)
        # First argument, filter input, is implied.
        plen = len(provided) + 1
        # Check to see if a decorator is providing the real function.
        func = inspect.unwrap(func)

        args, _, _, defaults, _, _, _ = inspect.getfullargspec(func)
        alen = len(args)
        dlen = len(defaults or [])
        # Not enough OR Too many
        if plen < (alen - dlen) or plen > alen:
            raise TemplateSyntaxError(
                "%s requires %d arguments, %d provided" % (name, alen - dlen, plen)
            )

        return True

def resolve(self, context, ignore_failures=False)
django.template.base.FilterExpression 
    def resolve(self, context, ignore_failures=False):
        if self.is_var:
            try:
                obj = self.var.resolve(context)
            except VariableDoesNotExist:
                if ignore_failures:
                    obj = None
                else:
                    string_if_invalid = context.template.engine.string_if_invalid
                    if string_if_invalid:
                        if "%s" in string_if_invalid:
                            return string_if_invalid % self.var
                        else:
                            return string_if_invalid
                    else:
                        obj = string_if_invalid
        else:
            obj = self.var
        for func, args in self.filters:
            arg_vals = []
            for lookup, arg in args:
                if not lookup:
                    arg_vals.append(mark_safe(arg))
                else:
                    arg_vals.append(arg.resolve(context))
            if getattr(func, "expects_localtime", False):
                obj = template_localtime(obj, context.use_tz)
            if getattr(func, "needs_autoescape", False):
                new_obj = func(obj, autoescape=context.autoescape, *arg_vals)
            else:
                new_obj = func(obj, *arg_vals)
            if getattr(func, "is_safe", False) and isinstance(obj, SafeData):
                obj = mark_safe(new_obj)
            else:
                obj = new_obj
        return obj