Writing Defaultdict(list) To File

Previously asked a question Using defaultdict to parse multi delimiter file While I do get the desired output based on the code, I am struggling to write it to a file as a table in

Solution 1:

I would do this (python 2):

with open('mycsvfile.csv', 'wb') as f:  # binary is better, avoids blank lines in some python 2 versions
    writer = csv.writer(f,delimiter="\t")
    keys=["count","pos","_pos","_neg"]
    writer.writerow([""]+keys)
    for k, vl in ids.iteritems():
        for v in vl:
            writer.writerow([k] + [v[key] for key in keys])

you need a double loop to iterate on the lists for each key. I have stored the column names in a list, so I can reuse it to build the rows in a list comprehension & for the title as well (first item doesn't have a title, I just left it blank)

now it looks like this:

        count   pos     _pos    _neg
31022550        0       20      0       0
31022550        2       20      2       0
31022550        0       20      0       0

(slightly shifted because tab character isn't wide enough, but not an issue to read it back)

Python 3 users would have to change:

withopen('mycsvfile.csv', 'wb') as f:

by

withopen('mycsvfile.csv', 'w',newline="") as f:

and

fork, vl in ids.iteritems():

by

for k, vl in ids.items():  # also works in python 2

note that the writerow double loop could be replaced by a single line, a double-loop, flat generator comprehension passed to writerows, faster to execute:

writer.writerows([k] + [v[key] forkeyin keys] fork, vl in ids.items() forvin vl)