KeyError Filling Defaultdict Python

Question

I am attempting to fill a default dictionary with csv data, and I am getting a key error

for i in range(0,1):

    #https://docs.python.org/2/library/collections.html#collections.defaultdict
    result = co.defaultdict(list)
    with open(os.path.join(inputdir,tablelist[i])) as f:

        csv_reader = csv.reader(f)
        csv_headings = next(csv_reader)
        read = csv.DictReader(f)

        for line in read:
            for j in range(1,len(csv_headings)):
  error here--->result[line[csv_headings[0]]].append(line[csv_headings[j]])  

for csv data

API,CNTYNM,PRMT,
4700100002,Barbour,2,
4700100003,Barbour,3,
4700100004,Barbour,4,

the key error is for API which means to me that something with dictreader is not working as expected can anyone give some advice?

Answer 1

You are missing fieldnames argument to DictReader. If you modify your code to pass csv_haedings to DictReader it will work (hopefully as expected):

for i in range(0,1):

    #https://docs.python.org/2/library/collections.html#collections.defaultdict
    result = co.defaultdict(list)
    with open(os.path.join(inputdir,tablelist[i])) as f:

        csv_reader = csv.reader(f)
        csv_headings = next(csv_reader)
        read = csv.DictReader(f, fieldnames=csv_headings)

        for line in read:
            for j in range(1,len(csv_headings)):
                result[line[csv_headings[0]]].append(line[csv_headings[j]])