CODEWITHSUNDEEP
pythondjango
Alex Lord Mordor
Alex Lord Mordor

Reputation: 3040

Django/Python Chain and Sort Querysets

I have an inventory count that has N locations, this locations needs to be counted N times, so I have one model for "the location header" and another for the item list of every header.

I need to chain,sort AND get unique results of the items in N querysets

I have this:

loc_id = request.POST['loc_id'] # the Id of my location pivot
inv_location = InventoryLocations.objects.get(pk=loc_id) # get the location count pivot
inv_locations = InventoryLocations.objects.filter(location=inv_location.location,
                inventory=inv_location.inventory) #get all related locations counts

# At this point i can have N inv_locations

count_items = [] # list of items in all inventory counts 
for l in inv_locations:
    items = InventoryDetails.objects.filter(inventory_location = l) # get items of every count 
    count_items.append(items)

# Now I have all the items counted in the counts_items array, I need to get from this a single
# list of items Ordered and not repeated    

all_items = chain(count_items) <<< IS THIS CORRECT??
sorted_items = sorted(all_items,key=lambda item: item.epc) << THIS GIVE ME ERROR
unique_items = ???

My models are:

class InventoryCount(models.Model):
    ...nothing important

class InventoryLocation(models.Model):
    inventory= models.ForeignKey(InventoryCount)
    location= models.ForeignKey(Location)
    ...

class InventoryDetails(models.Model):
    inventory_location= models.ForeignKey(InventoryLocations)
    epc = models.CharField(max_length=25, null=True, blank=True)
    item= models.ForeignKey(Item)
    ...

Basically, I need a list of all items counted in all inventoryDetails in the array sorted by epc and not repeated

I'm stuck in here, i dont know if the chain is doing it right and the sort function gives me an error saying that the item has no 'epc' attribute.

Help plz!

Upvotes: 0

Views: 1220

Answers (1)

Peter DeGlopper
Peter DeGlopper

Reputation: 37319

To solve your immediate problem - assuming that's itertools.chain, chain takes multiple iterables. Use chain(*count_items) to expand your list of querysets.

But you can save yourself some trouble by using InventoryDetails.objects.filter(inventory_location__in=inv_locations).order_by('epc').distinct() - that'll do the sorting and uniquing in the database rather than you doing it in your view.

Upvotes: 1

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