Too many values to unpack in multi dictionary

Question

I'm importing data from .csvs and creating a lot of data dictionaries. My code is based off someone else's work with a dataset that has substantially fewer columns than mine. I'll show both her code and then mine and then the error I'm receiving. Original Code:

capacitya = open('C:/Users/Nafiseh/Desktop/Book chapter-code/arc-s.csv', 'r')
csv_capacitya = csv.reader(capacitya)
mydict_capacitya = {}
for row in csv_capacitya:
    mydict_capacitya[(row[0], row[1],row[2])] = float(row[3])

My modification:

# arc capacity
capacitya = open('C:/Users/Emma/Documents/2021-2022/Thesis/Data/arcs.csv', 'r')
csv_capacitya = csv.reader(capacitya)
mydict_capacitya = {}
for row in csv_capacitya:
    mydict_capacitya[(row[0], row[1],row[2])] = list(row[3:22])

When I run this later segment of code:

   # arc capacity
capacitya = open('C:/Users/Emma/Documents/2021-2022/Thesis/Data/arcs.csv', 'r')
csv_capacitya = csv.reader(capacitya)
mydict_capacitya = {}
for row in csv_capacitya:
    mydict_capacitya[(row[0], row[1],row[2])] = list(row[3:22])
#print(mydict_capacitya)
capacityaatt = open('C:/Users/Emma/Documents/2021-2022/Thesis/Data/distarc.csv', 'r')
csv_capacityaatt = csv.reader(capacityaatt)
mydict_capacityaatt = {}
for row in csv_capacityaatt:
    mydict_capacityaatt[(row[0], row[1],row[2])] = float(row[3])

attarc, capacityatt= multidict(mydict_capacityaatt)
attarc = tuplelist(attarc)
arc, capacitya = multidict(mydict_capacitya)

Error:

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-29-66e3074f2135> in <module>
    120 attarc, capacityatt= multidict(mydict_capacityaatt)
    121 attarc = tuplelist(attarc)
--> 122 arc, capacitya = multidict(mydict_capacitya)
    123 

ValueError: too many values to unpack (expected 2)

If it helps, both in the original code and in my modification, columns [0:2] represent [k,i,j]. In the original dataset, column [4] represented the value. In the updated dataset, columns [3:22] represent values on the new index g. That is, column [4] represents values when g = 2, for example. Thanks!

Edit: Added more relevant segments of code