[Tutor] A CSV field is a list of integers - how to read it as such?

[DoanVietTrungAtGmail]

Dear tutors

I am checking out csv as a possible data structure for my records. In each
record, some fields are an integer and some are a list of integers of
variable length. I use csv.DictWriter to write data. When reading out using
csv.DictReader, each row is read as a string, per the csv module's standard
behaviour. To get these columns as lists of integers, I can think of only a
multi-step process: first, remove the brackets enclosing the string;
second, split the string into a list containing substrings; third, convert
 each substring into an integer. This process seems inelegant. Is there a
better way to get integers and lists of integers from a csv file?

Or, is a csv file simply not the best data structure given the above
requirement? Apart from csv, I considered using a dict or list, or using an
object to represent each row. I am being attracted to csv because csv means
serialisation is unnecessary, I just need to close and open the file to
stop and continue later (it's a simulation experiment). Also, I am guessing
but haven't checked, csv is more space efficient. Each row contains a few
integers plus a few lists containing hundreds of integers, and there will
be up to hundreds of millions of rows.

CODE: My Python 2.7 code is below. It doesn't have the third step
(substring -> int).

import csv

record1 = {'id':1, 'type':1, 'level':1, 'ListInRecord':[2, 9]}
record2 = {'id':2, 'type':1, 'level':1, 'ListInRecord':[1, 9]}
record3 = {'id':3, 'type':2, 'level':1, 'ListInRecord':[2]}
record9 = {'id':9, 'type':3, 'level':0, 'ListInRecord':[]}
rows = [record1, record2, record3, record9]
header = ['id', 'type', 'level', 'ListInRecord']

with open('testCSV.csv', 'wb') as f:
    fCSV = csv.DictWriter(f, header)
    fCSV.writeheader()
    fCSV.writerows(rows)

with open('testCSV.csv', 'r') as f:
    fCSV = csv.DictReader(f)
    for row in fCSV:
        print 'ID=', row['id'],'ListInRecord=',
row['ListInRecord'][1:-1].split(', ') # I want this to be a list of
integers, NOT list of strings

OUTPUT:

ID= 1 ListInRecord= ['2', '9']
ID= 2 ListInRecord= ['1', '9']
ID= 3 ListInRecord= ['2']
ID= 9 ListInRecord= ['']

Trung Doan
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