如何在.csv中将“，”指定为3个字符的分隔符字符串？

Question

How to specify (when reading a file) and assign (in output) this 3-character string "," as .csv delimiter? For example: "col1","col2","col3","col4"

The code where it needs to be used for reading and output:

import csv
with open('a.csv', 'r') as infile, open('reordered.csv', 'a') as outfile:
    fieldnames = ['B', 'C', 'A', 'D']
    writer = csv.DictWriter(outfile, delimiter=',', fieldnames=fieldnames)
    writer.writeheader()
    for row in csv.DictReader(infile):
        writer.writerow(row)

I tried to look it up ( https://docs.python.org/2.0/ref/strings.html ), etc. but it is not clear.

UPDATE: As pointed out by others, this may not be "," delimiter, but a , delimiter and "values" . Regardless, my values contain commas , , so the "," pattern between columns helps to maintain column structure.

Answer 1

You'll want to define the quote character , setting the delimiter will not get you the desired results.

import csv
with open('a.csv', 'r') as f:
    reader = csv.reader(f, delimiter=',', quotechar='"')
    for row in reader:
        print row

Edit: As for changes to your code, it would look somewhat like this:

with open('a.csv', 'r') as infile, open('reordered.csv', 'a') as outfile:
    fieldnamesout = ['B', 'C', 'A', 'D']
    fieldnamesin = ['A', 'B', 'C', 'D']
    reader = csv.DictReader(infile, delimiter=',', quotechar='"', fieldnames=fieldnamesin)
    writer = csv.DictWriter(outfile, delimiter=',', quotechar='"', fieldnames=fieldnamesout, quoting=csv.QUOTE_ALL)
    for row in reader:
        writer.writerow(row)

Note the quoting=csv.QUOTE_ALL , which instructs the writer to quote all fields according to the quotechar , this may or may not be what you want, other options would be quoting=csv.QUOTE_NONNUMERIC .

Answer 2

Seems like your values are string literals. I don't know if the cvs module can handle this out of the box. It is not a parsing problem it is a data processing problem.

Your values are in the quote chars. So either you truncate them when processing your data field_value.replace('"', '') and add them back later on '"{}"'.format(field_value) or you straight operate on the data fields leaving the quote char in place.