python - How do you catch this exception? -

This code is in the Django / DB / Models / Areas / makes an exception / defines it? class reversaling related object descriptor (six.we_metallacles (named object object descriptor method)): # This class provides functionality that provides related objects # Managers with attributes on model class Is available in the form, for which there is a single "remote" value for the category which defines the related field #for example "choice.poll", the pole attribute is a #reversing signal Layered object descriptor is example. Def __init __ (self, field_with_rel): self.field = field_with_rel self.cache_name = self.field.get_cache_name () @ cached_property def related object dots notexist (self): # Exception can not be made at the initial time because the # related model To be solved yet; `Rel.to` can still be the # string model reference, return type (str ('related object dot notexist'), (selffield, rlt.donotexist, attribute error), {})

This is in the Django / DB / Model / field / related. The PC raises the above exception:

  def __get __ (self, example, example_type = none): if Example is none: Returns the self attribute: rel_obj = getattr (e.g., self.cache_name) except AttributeError: val = self.field.get_local_related_value ( If any is not in Val: rel_obj = any other not: params = dict (rh_field.attname, getattr (for example, lh_field.attname)) for lh_field, self.field in rh_field. If Eaststens (extra_filters, dict ): Params.update (extra_filter) qs = qs.filter (** parameter) Other: qs = Qs.filter (extra_filter, ** params) # Imposes foreign key while assuming the database, it will not fail. Rel_obj = Qs.get () If not self.field.rel.multiple: setattr (rel_obj, self.field.related.get_cache_name (), example) setattr (example, self.cache_name, rel_obj) if rel_obj no one and not itself field.null: self Dhaan. No related objectNotClass ("% s has no% s."% (Self.field.model.__name__, self.field.name)) Other: Return rel_obj   
 The problem is Try this code:  
  Try: related to except val = getattr (obj, attr_name) Rawsingal Related Object Descriptor Addressed ObjectDoesNotExist: Val = None # Throwing Exceptions Causes   
 isinstance (foo, related.FieldDoesNotExist) Foo except for exceptions: Foo type: Foo # Catch here, Not above  
 will not catch that exception  
  & gt; & Gt; & Gt; Print Type (foo) & lt; Class 'django.db.models.fields.related.RelatedObjectDoesNotExist' & gt; Except related to   
 and  
  .related object dots notexist:   
 one raises  AttributeError: The 'module' object is any specialty 'related object dot notexist'.   
  & gt; & Gt; isinstance (foo, related .reverseSingleRelatedObjectDescriptor.RelatedObjectDoesNotExist) traceback (most recent call final): File "& lt; string & gt;" , Line 1, & lt; Fragment & gt; TypeError: isinstance () arg 2 should be a class, type, or type of type and type   
 which is probably the reason for this.   
 
 
 If your respective model is called Fu, then you can:  < Except for pre>  Foo.DoesNotExist:   
 Dango is amazing when it is not awesome  related object dots notexist  is a property that is dynamic on runtime Gives the type to be traced that type  self.field.rel.to.DoesNotExist uses  as a base class according to the Django document:  
 
  
 Exceptions  DoesNotExist   
  DoesNotExist  has been lifted when an object for a given parameter is not found for Django as a model of a model  DoesNotExist  provides an exception for which to identify the range of the object and leave you   try  /    .   
 It is such a magic that does this. Once the model has been created, then  self.field.rel.to.DoesNotExist  is not present for that model is an exception.