# cherrypy._helper module

Helper functions for CP apps.

class cherrypy._helper._ClassPropertyDescriptor(fget, fset=None)

  Bases: `object`

  Descript for read-only class-based property.

  Turns a classmethod-decorated func into a read-only property of that class type (means the value cannot be set).

cherrypy._helper.classproperty(func)

  Decorator like classmethod to implement a static class property.

cherrypy._helper.expose(func=None, alias=None)

  Expose the function or class.

  Optionally provide an alias or set of aliases.

cherrypy._helper.normalize_path(path)

  Resolve given path from relative into absolute form.

cherrypy._helper.popargs(*args, **kwargs)

  Decorate _cp_dispatch.

  (cherrypy.dispatch.Dispatcher.dispatch_method_name)

  Optional keyword argument: handler=(Object or Function)

  Provides a _cp_dispatch function that pops off path segments into cherrypy.request.params under the names specified. The dispatch is then forwarded on to the next vpath element.

  Note that any existing (and exposed) member function of the class that popargs is applied to will override that value of the argument. For instance, if you have a method named “list” on the class decorated with popargs, then accessing “/list” will call that function instead of popping it off as the requested parameter. This restriction applies to all _cp_dispatch functions. The only way around this restriction is to create a “blank class” whose only function is to provide _cp_dispatch.

  If there are path elements after the arguments, or more arguments are requested than are available in the vpath, then the ‘handler’ keyword argument specifies the next object to handle the parameterized request. If handler is not specified or is None, then self is used. If handler is a function rather than an instance, then that function will be called with the args specified and the return value from that function used as the next object INSTEAD of adding the parameters to cherrypy.request.args.

  This decorator may be used in one of two ways:

  As a class decorator:

      @cherrypy.popargs('year', 'month', 'day')
      class Blog:
          def index(self, year=None, month=None, day=None):
              #Process the parameters here; any url like
              #/, /2009, /2009/12, or /2009/12/31
              #will fill in the appropriate parameters.

          def create(self):
              #This link will still be available at /create.
              #Defined functions take precedence over arguments.

  Or as a member of a class:

      class Blog:
          _cp_dispatch = cherrypy.popargs('year', 'month', 'day')
          #...

  The handler argument may be used to mix arguments with built in functions. For instance, the following setup allows different activities at the day, month, and year level:

      class DayHandler:
          def index(self, year, month, day):
              #Do something with this day; probably list entries

          def delete(self, year, month, day):
              #Delete all entries for this day

      @cherrypy.popargs('day', handler=DayHandler())
      class MonthHandler:
          def index(self, year, month):
              #Do something with this month; probably list entries

          def delete(self, year, month):
              #Delete all entries for this month

      @cherrypy.popargs('month', handler=MonthHandler())
      class YearHandler:
          def index(self, year):
              #Do something with this year

          #...

      @cherrypy.popargs('year', handler=YearHandler())
      class Root:
          def index(self):
              #...

cherrypy._helper.url(path='', qs='', script_name=None, base=None, relative=None)

  Create an absolute URL for the given path.

  If ‘path’ starts with a slash (‘/’), this will return

    (base + script_name + path + qs).

  If it does not start with a slash, this returns

    (base + script_name [+ request.path_info] + path + qs).

  If script_name is None, cherrypy.request will be used to find a script_name, if available.

  If base is None, cherrypy.request.base will be used (if available). Note that you can use cherrypy.tools.proxy to change this.

  Finally, note that this function can be used to obtain an absolute URL for the current request path (minus the querystring) by passing no args. If you call url(qs=cherrypy.request.query_string), you should get the original browser URL (assuming no internal redirections).

  If relative is None or not provided, request.app.relative_urls will be used (if available, else False). If False, the output will be an absolute URL (including the scheme, host, vhost, and script_name). If True, the output will instead be a URL that is relative to the current request path, perhaps including ‘..’ atoms. If relative is the string ‘server’, the output will instead be a URL that is relative to the server root; i.e., it will start with a slash.