Dictionary of Lists to CSV in Python

Question

I currently have a dictionary who values are lists.

Example: {1: [12, 13, 14, 15], 2: [12, 13, 14, 15], 3: [12, 13, 14, 15]} and so on.

I have 20000 keys, and each list contains 80 values.

I am trying to output this into a CSV file, but have had no luck using Dictwriter. Here is part of my code:

for i in range(0, 3):

    filetxt = "\\Level_3\\" + nonsbar[i]
    filedata = list(csv.reader(open(filetxt,'rb'), delimiter='\t'));

    for j in range (1, len(filedata)):
        tempid = filedata[j][0]
        idind = tempid.index('|')
        geneid = tempid[idind+1:len(tempid)]
        genecount = filedata[j][1]
        nconn[geneid].append(genecount)


for keys in nconn.keys():
    nconn[keys] = zip(nconn[keys])

print "convert to table"
nkeys = nconn.keys()
filetxt = open('nonsmoke.csv', 'wb')
nonsmoketab = csv.DictWriter(filetxt, nkeys,delimiter=',')
nonsmoketab.writeheader()
nonsmoketab.writerow(nconn)

I get an ouput like this:

114787  114786  
[('161.00',), ('985.00',), ('68.00',)]  [('9.00',), ('19.00',), ('2.00',)]

I instead want this:

114787 114786   
161     9
985     19
68      2

alko · Accepted Answer · 2013-12-24 06:58:59Z

3

Do you want to transpose your dictionary of lists? You can do it with itertools.izip_longest for example:

from itertools import izip_longest
d = {1: [12, 13, 14, 15], 2: [16, 17, 18], 3: [19, 20, 21, 22]}
labels = d.keys()
rows = izip_longest(*d.values())

You can use csv.writer to serialize back to csv:

import StringIO
buf = StringIO.StringIO()
outf = csv.writer(buf)
outf.writerow(labels)
outf.writerows(rows)
print buf.getvalue()
# 1,2,3
# 12,16,19
# 13,17,20
# 14,18,21
# 15,,22

edited Dec 24, 2013 at 6:58

answered Dec 24, 2013 at 6:52

alko

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2 Comments

rmehta1987 Over a year ago

Thanks! This worked perfectly. Out of curiosity is there a more efficient way of handling all this data, I want to use python for some bayes-net, but I have to discretize the data first.

alko Over a year ago

@user3131429 you should start a separate thread for a separate question, and describe it in full detail. At least this is free :) and welcomed as long as you're ontopic. Standard disclaimer, if you found answer useful and serving your needs, cosider accepting it.

feifan.overflow · Accepted Answer · 2013-12-24 06:40:04Z

0

I can give you a rough advise: implement from csv.DictWriter, overwrite method writerow(self, rowdict) and writerows(self, rowdicts), add loop on the result from self._dict_to_list(rowdict)(it's list in your case) in these 2 functions.

answered Dec 24, 2013 at 6:40

feifan.overflow

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