Working with Table and Row objects?

Anvil Q&A
1

I often want to inspect Table and Row objects. Four things I’m trying to do and their gross workarounds:

‘Get’ from a row object if the column exists:

if 'my_column' in dict(row_object):
    value = row_object['my_column']
else:
    value = None

Find out if an object is a row object:

hasattr(row_object, 'get_id') 
# type(row_object) gives anvil._server.LiveObjectProxy

There must be a better way!! Any ideas?

SOLVED:
Credit to stucork:
Figure out the Table a row is associated with:

tables = [app_tables.Table1, app_tables.Table2]
for table in tables:
    if table.has_row(row_object)
        break
else: # no break
    raise Exception('row does not exist in any known table')

Credit to campopiano:
Figure out the columns in a table:

columns = app_tables.MyTable.list_columns()
# This returns a dict of columns and field types
2

Some ideas that come to mind:

list_columns() I’ve never used it but I believe you pass the table object in as an argument. You could extrapolate that to also find the columns associated with a table (your 1st question).

If the row object is a dict, I think you can go:

value = my_dict_row.get('some_key', <someDefaultValue>)
3

Thanks campopianoa!

Great find on the list_columns method of app_table objecsts! That checks that one off the list…

Row objects are ‘dict-like’ but they don’t have a get method (I definitely think they should)! Conversion of row objects to dictionaries causes other problems.

Dan

4

You can pass a row to the dict function and then use get on the resulting object.

5

As an alternative to 1 - tables have a has_row method.

tables = [app_tables.Table1, app_tables.Table2]
for table in tables:
    if table.has_row(row_object)
        break
else: # no break
    raise Exception('row does not exist in any known table')

Noted on the request to add useful dict-like methods to row objects.

1 Like
6

Thanks Owen!

I am under the impression that this costs an additional server-call (if done client-side). Is anyone able to confirm/deny?

7

Great, thanks stucork! I will take this as a solution since it’s significantly less gross… but suggest that it would be helpful if we could get the table directly from the row object somehow!

8

You might want to upvote this feature request

9

Since you already know the name of the type of object, one ‘less gross’ standard way is isinstance():

isinstance( row_object, anvil._server.LiveObjectProxy )

…will yield a boolean value of True :cake:

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