Writing defaultdict to CSV file

Question

I have a defaultdict being written to file like this:

writer = csv.writer(open(locationToSaveFile, 'wb+')) 
for k,v in dict.iteritems():
 writer.writerow([k ,v])

I then have this horribly convoluted text to read it back in:

myDict = defaultdict(list) 
with open(fileLocation, 'rb') as test:
 reader = csv.DictReader(test, ['processedText', 'date'])
 for line in reader:
 myDict[line['processedText']].append(line['date'])
textDict = defaultdict(list) 
for processedText, date in myDict.items():
 actual_list = ast.literal_eval(date[0])
 for a in actual_list:
 textDict[processedText].append(a)
for processedText, date in textDict.items(): 

Obviously this looks very wasteful (and looks horrible!) but I don't know how else to import the defaultdict.

When opening it with the reader = and for line in reader lines it creates a list within a list. The only way out of this is to use ast to convert it.

Could somebody advise me how to tidy this up?

Note: I'm very unfamiliar with Python

Answer 1

csv is meant to store rows of data, not a simple dictionary. You can use json for that:

import json
# writing
json.dump(yourdict, open(filename, 'w'))
# reading
yourdict = json.load(open(filename))

• Andrew Martin: How do I read it back from JSON. I can write it using json.dump(filelocation, defaultdict). But how do I import it again?
• Mischa Arefiev: Andrew, use json.load(filelike_object)

Answer 2

Your dict's values are lists. A possible approach is to expand those lists into csv columns, producing a file where the number of columns varies from row to row:

#writing
with open(locationToSaveFile, 'w') as f:
 writer = csv.writer(f) 
 for k,v in mydict.iteritems():
 writer.writerow([k] + v)
#reading
with open(locationToSaveFile, 'r') as f:
 reader = csv.reader(f) 
 mydict = collections.defaultdict(list)
 for row in reader:
 mydict[row[0]] = row[1:]