Unique values in column

Anvil Q&A
1

I am trying to make a dropdown list with only the unique elements from a column in a table. I tried different solutions but keep ending up with the full list with the same values repeating it self.

the boilerblate:

  def drop_down_1_show(self, **event_args):
    """This method is called when the DropDown is shown on the screen"""
    searchitem = [(r['Ejendom'],r) for r in app_tables.inst.search()]
    self.drop_down_1.items = searchitem

one attemp:

  def drop_down_1_show(self, **event_args):
    """This method is called when the DropDown is shown on the screen"""
    searchitem = [(r['Ejendom'],r) for r in app_tables.inst.search()]
    searchitem = list(dict.fromkeys(searchitem))
    self.drop_down_1.items = searchitem

I also tried itterating through the list but it didn’t work either

  def drop_down_1_show(self, **event_args):
    """This method is called when the DropDown is shown on the screen"""
    searchitemlist = set()
    searchitem = [(r['Ejendom'],r) for r in app_tables.inst.search()]
    for x in searchitem:
      searchitemlist.add(x)   
    #searchitem = list(dict.fromkeys(searchitem))
    self.drop_down_1.items = searchitemlist

also tried

searchitem = [(r['Ejendom'],r) for r in app_tables.inst.search()]
used = []
for x in searchitem:
  if x in used:
    searchitem.delete(x)
  else:
    used.append(x)
self.drop_down_1.items = used
2

A common technique for creating lists of unique values is to create a set and pass that set to the list function.

In your boilerplate example, that might look something like:

def drop_down_1_show(self, **event_args):
    """This method is called when the DropDown is shown on the screen"""
    searchitem = list({(r['Ejendom'],r) for r in app_tables.inst.search()})
    self.drop_down_1.items = searchitem

(I converted your original list comprehension to a set comprehension and passed that to the list function).

2 Likes
3

Note: because row r is present in each tuple, each tuple will be unique, even if r['Ejendom'] is not.

Did you want only distinct values of r['Ejendom']?

4

Yes you are right. only distinct values.
I tried making a code in repl that iterates over a list. But this metode dosnt work in anvil.
Thanks alot for the explanation. I was starting to think it might be something like this but I didnt know how to make a solution.

https://repl.it/join/nqpuuvav-wikinggaffa

5

Thanks for the example! This helps me alot.
I tried some solutions with list and set.

6

I didn’t get it to work. I still get a list with the same value repeated several times

image
image1339×507 17 KB

7

@p.colbert @owen.campbell

Silly me… I didn’t need r in the line at all. I got it to work. Thanks to your explanations.

This was all that was needed!

  def drop_down_1_show(self, **event_args):
    searchitem = list(set([(r['Ejendom']) for r in app_tables.inst.search()]))
    self.drop_down_1.items = searchitem
1 Like
8

I wonder if a set comprehension would suffice here. That is, instead of

list(set([(r['Ejendom']) for r in app_tables.inst.search()]))

how about

list( { r['Ejendom']  for r in app_tables.inst.search() } )

? This should build a set of strings directly, instead of through an intermediate list.