topic Re: Update Cursor/If Statement in Python Questions

Update Cursor/If Statement

ThiPham12 — Mon, 09 Aug 2021 04:40:01 GMT

I am trying to use the Update Cursor to look-up a key in a dictionary I created, Region_dic and if it finds the key, it will update the row with the value. However, for some reason, the if statement equals false, when it should be true. Thanks for your help!

keyRegion='directory pathway'

with arcpy.da.UpdateCursor(keyRegion,["Region","ID"]

for row in cursor:

if row[0] in Region_dic:

row[1]==Region_dic.get(row[0])

cursor.updateRow(row)

Re: Update Cursor/If Statement

DavidPike — Mon, 09 Aug 2021 09:16:38 GMT

maybe a case issue or whitespace? Maybe ditch the cursor for a moment and just add some print statements to debug.

Re: Update Cursor/If Statement

broy06 — Mon, 09 Aug 2021 10:23:02 GMT

Hi, Try to use print statement before cursor.updateRow(row). so that if there is an error you'll find it.

Re: Update Cursor/If Statement

JohannesBierer — Mon, 09 Aug 2021 11:42:21 GMT

In my opinion you will have to loop the dictionary as well to find the right key? Maybe try something like this?

with arcpy.da.UpdateCursor(keyRegion,["Region","ID"]) as cursor: for row in cursor: for key, value in Region_dic.iteritems(): if key == row[0]: print key, value row[1] = value cursor.updateRow(row) else: print ("does not fit")

Re: Update Cursor/If Statement

Anonymous User — Mon, 09 Aug 2021 12:42:45 GMT

The 'if row[0] in Region_dic' and Region_dict.get() methods iterate through/ lookup the dictionary already.

I'd wonder if the key types are the same between the dictionary and the row[0] value being checked as well as what @DavidPike said with Case differences.

with arcpy.da.UpdateCursor(keyRegion,["Region","ID"]) as cursor: for row in cursor: val = Region_dic.get(row[0], 'Not Found') # you can set this to default to other default values (like the default None) if the key is not found in the dict. if val != 'Not Found': row[1] = val cursor.updateRow(row) else: print(f'{row[0]} was not found. Check the dictionary keys for differences.')

Re: Update Cursor/If Statement

JohannesLindner — Wed, 11 Aug 2021 12:10:25 GMT

I think you copied your code wrong, but just in case:

The first line is incomplete (closing paranthesis and "as cursor:")

row[1]==Region_dic.get(row[0]) # You're using two equal signs, which compares row[1] to Region_dic[row[0]]; # this line will compute to True or False, but it won't set row[1]. # what you want is this: row[1] = Region_dic.get(row[0])

You actually don't need the manual check for the key, you can just catch the KeyError:

keyRegion = 'directory pathway' with arcpy.da.UpdateCursor(keyRegion, ["Region","ID"]) as cursor: for r, i in cursor: try: i = Region_dic[r] cursor.updateRow([r, i]) except KeyError: print("{} was not found.".format(r))

Re: Update Cursor/If Statement

ThiPham12 — Thu, 12 Aug 2021 02:33:00 GMT

HI Prabal,

Thanks for your help. When I add the else: 'not found', the result is not found. When I tried the print statement: print('row[0] not found'), there is an error "error return without exception set."