I have a field that holds a variety of strings. These strings were field names and corresponding values that were concatenated into a single field per feature. Using .split/indexing I was able to create a dictionary where values correspond to field names and values correspond to attributes.

attributes in field= '"xyz"="abc","ghi"="lmno"'

dict= {'xyz':'abc','ghi':'lmno'}

I am now at the point where I'm trying to feed the keys:values into a da.UpdateCursor where the key is the field and row= value. Block below is the last part of the script I'm struggling with. I keep getting an error: sequence size must match size of row.

i= 0
z= 0
n= 0

while i <= getCount:
    kI= dic.keys()[z]
    kiS= str(kI)
    vI= dic.values()[n]

    with arcpy.da.UpdateCursor(item,kiS)as cursor:
        for row in cursor:
            row= vI
            i+= 1
            z+= 1
            n+= 1
  • 1
    It looks like it's at row = vI, it should be something like row[n] = vI. I would use the dictionary as-is rather than iterating as all your features would have the last value in the dictionary. Mar 17, 2017 at 1:14
  • 1
    Clobbering the row variable is very inappropriate.
    – Vince
    Mar 17, 2017 at 1:14
  • Also should point out that you define your dictionary as dict yet refer to it as dic later on in your while loop. It's also not a good idea to call your dictionary 'dict' because it is a python key word.
    – Fezter
    Mar 17, 2017 at 1:17
  • Thanks for the comments. I attempted earlier to use the row[n] with no success. And although I used dict for the written portion above it is referenced as dic throughout the extent of the written script. Mar 17, 2017 at 1:19

1 Answer 1


I believe you're trying to do something like this:

dict= {'xyz':'abc','ghi':'lmno'}

for key in dict.iterkeys():
    print key + "=" + dict[key]
    with arcpy.da.UpdateCursor(item,key) as cursor:
        for row in cursor:
            row[0] = dict[key]

Updating each field with the value stored against it in the dictonary.. It would be better to update each field in the row in turn and store once:

dict= {'xyz':'abc','ghi':'lmno'}

with arcpy.da.UpdateCursor(item,list(dict.iterkeys())) as uCur: # list(dict.iterkeys()) is ['xyz','ghi']
    fRange = range(len(dict))    # range to iterate - in this case [0,1]
    fVals  = list(dict.values()) # list of values   - in ths case ['abc','lmno']
    for row in UCur:
        for Index in fRange:     # update each field by index in the lists
            row[Index] = fVals[Index]

As the slowest part is the storing of the row this will work much quicker.

  • thanks so much. I'll try first thing tomorrow when get access to a computer with arc on it. I'll be sure to accept this as soon as I can. Mar 17, 2017 at 1:29
  • Just create a list outside of the for loop. It never changes because the field order is static...
    – Paul
    Mar 17, 2017 at 5:04
  • After running it hit an error stating for Index in fRange: TypeError: 'int' object is not iterable. Although I'm not sure of the hit on performance for doing this, prior I was able to run using while..in this case it would look like Index= 0 while Index <= fRange: row[Index]=fVals[Index] Index +=1. Will try to update with this later today unless you think there may be a way that will perform it better. Thanks Mar 17, 2017 at 17:54
  • Sorry, I forgot the range keyword. len(dict) returns an int which is not iterable but range(len(dict)) returns a range from 0 to the length of the dict minus one. I've fixed that in the code. Mar 19, 2017 at 21:51

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