python csv - not closing file

Question

im reading a csv file and then writing a new one:

import csv

with open('thefile.csv', 'rb') as f:
  data = list(csv.reader(f))

import collections
counter = collections.defaultdict(int)
for row in data:
    counter[row[11]] += 1

writer = csv.writer(open('/pythonwork/thefile_subset1.csv', 'w'))
for row in data:
    if counter[row[11]] >= 500:
       writer.writerow(row)

for some reason i cannot get the csv.writer to close the file. when i open the file it opens it as READ ONLY because it says that is still open.

how do i close thefile_subset1.csv after i am done with it?

Answer 1

You can break out the open command into its own variable, so that you can close it later.

f = open('/pythonwork/thefile_subset1.csv', 'w')
writer = csv.writer(f)
f.close()

csv.writer throws a ValueError if you try to write to a closed file.

Answer 2

Force the writer to clean up:

del writer

Answer 3

Look at the difference:

with open('thefile.csv', 'rb') as f:
    data = list(csv.reader(f))

vs:

writer = csv.writer(open('/pythonwork/thefile_subset1.csv', 'w'))

Answer 4

with open('/pythonwork/thefile_subset1.csv', 'w') as outfile:
    writer = csv.writer(outfile)
    for row in data:
        if counter[row[11]] >= 500:
           writer.writerow(row)