[FIXED] How do I invalidate @cached_property in django

Issue

I am currently using @cached_property on a model class and I would like to delete it on save so that it can be repopulated on the next call. How do I do this? Example:

class Amodel():
    #...model_fields....

    @cached_property
    def db_connection(self):
        #get some thing in the db and cache here


instance = Amodel.objects.get(id=1)
variable = instance.db_connection

Amodel.objects.select_for_update().filter(id=1).update(#some variable)
#invalidate instance.db_connection
#new_variable = instance.db_connection

Thanks

Solution

Just del it as documentation says. It will lead to recalculation on next access.

class SomeClass(object):
    
    @cached_property
    def expensive_property(self):
         return datetime.now()

obj = SomeClass()
print obj.expensive_property
print obj.expensive_property # outputs the same value as before
del obj.expensive_property
print obj.expensive_property # outputs new value

For Python 3 it's the same use of del. Below is an example of a try/except block.

try:
    del obj.expensive_property 
except AttributeError:
    pass 

Answered By - isobolev