Python Cursors and Dictionaries- I am no Turbo Mechanic!

Question

using rfairhur24 very helpful blog on "Turbo Charging Data Manipulation with Python Cursors and Dictionaries", I have managed to create two separate libraries to compare to a cursors:

Comparison 1: Returns  records that are in table 'A' but not in Feature Class (FC) 'B' with the output being a list of fields    from table 'A' and a field stating that the record in table 'A" might need to be deleted. results in 4 records.

Comparison 2: To identify changed areas in table 'A' and FC 'B', with the output being key value and acreage from FC    'B'. results in 11 records.

using insertRow and setValue, I can get either of the cursor comparisons to write to Table 'c'. I can't get the script to write the first comparison and then write the second comparison, resulting in a change table with the two types of changes totaling 15 records.

I can hack code pretty good, but I obviously have a logic and reasoning issue when creating new code...

any help is greatly appreciated!!

RichardFairhurst · Answer

Glad it is working now and that both tables are now combined in the final output. The dictionary created in Line 16 was being changed after you ran Lines 19-21. The keys were the same, but the values associated with the keys are very different. In Line 16 the value associated with each dictionary key is a list containing values from Field B, Field C, Field D and Field E. After running Line 16, if you use the code table_a_data[row[0]]‍‍‍‍ the dictionary will return the list of field values, not a single field value. In order to get the value from just Field B from the list, a second set of brackets needs to be added with the index number of the value for Field B in the list (i.e. [0]). So, to directly call the value of Field B from the dictionary in one line of code you need to use table_a_data[row[0]]‍[0]‍‍ The list of field values associated with each dictionary key in Line 16 no longer existed after running lines 19-21. Lines 19-21 was changing the value associated with each dictionary key to being the value of Field B only. Therefore, after you ran Lines 19-21 you just needed to return the value associated with the dictionary key to get the value of Field B directly. You could have used two dictionaries to do the comparison in Lines 40-50, but you would need to use the dictionary created in Line 16, not the dictionary as modified by Lines 19-21. Instead of doing a for loop of the rows of the Table_A_Cursor, you would do a for loop of the keys of the table_a_data dictionary. Instead of assigning values to each field from row2 returned by the cursor, you would have assigned values to each field using the appropriate list index on the list returned from the table_a_data dictionary for each unmatched key, i.e. for key in table_a_dict: if not key in FC_B_data: insert = rows.newRow() insert.setValue("field D", table_a_dict[key][2]) insert.setValue("field C", table_a_dict[key][1]) insert.setValue("field B", table_a_dict[key][0]) insert.setValue("field E", table_a_dict[key][3]) insert.setValue("field F", 'NOT IN GIS:DELETE FROM Table_A?') rows.insertRow(insert) ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

GrahameRoss1 · Answer

cleaning up the code per your suggestions worked. there was not an error, it was not combining the two comparison outputs to the change table.

I don't remember where I got the syntax for lines 19-21... could you explain the second half of your line 23 to me? why the second bracketed zero in the '...table_a-data[row [0]][0]...'? the unique ID field I am comparing for both cursor and dictionary is [0] whereas the acreage to compare is for both is [1]. how does 'table_a-data [row[0]][0]' equate to [1]?

so I am using cursors and dictionaries... could I have done this just comparing the dictionaries?

Thank you for your help- I really appreciate your time!

RichardFairhurst · Answer

I think the real error is occurring because you are trying to create a newRow object using the SearchCursor row2 on line 42, which won't work. Line 42 needs to use the InsertCursor rows to create a newRow: insert = rows.newRow()‍‍ # Line 42‍‍‍‍‍‍‍