Update Cursor/If Statement

Question

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)

BeverlyPham · Answer

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."

JohannesLindner · Answer

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))

Anonymous User · Answer

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.')