gistfile1.py

from django import template

register = template.Library()

class PermissionNode(template.Node):
    def __init__(self, user, permission, variable_name, obj=None):
        self.user = template.Variable(user)
        self.permission = template.Variable(permission)
        if obj:
            self.obj = template.Variable(obj)
        else:
            self.obj = None
        self.variable_name = variable_name
    
    def render(self, context):
        user = self.user.resolve(context)
        permission = self.permission.resolve(context)
        
        if isinstance(self.obj, template.Variable):
            obj = self.obj.resolve(context)
        else:
            obj = self.obj
        
        context[self.variable_name] = user.has_perm(permission, obj)
        return ''

@register.tag
def has_permission(parser, token):
    """
    {% has_permission user permission [object] as variable_name %}
    """
    bits = token.contents.split()
    tag_name, user, permission = bits[0:3]
    
    if bits[3] == 'as':
        variable_name = bits[4]
        obj = None
    elif bits[4] == 'as':
        variable_name = bits[5]
        obj = bits[3]
    else:
        raise template.TemplateSyntaxError('%r should be in the format {%% user permission [object] as variable_name %%}.' % tag_name)
    
    return PermissionNode(user, permission, variable_name, obj)