How to apply regex sub to a csv file in python

Question

I have a csv file I wish to apply a regex replacement to with python.

So far I have the following

reader = csv.reader(open('ffrk_inventory_relics.csv', 'r'))
writer = csv.writer(open('outfile.csv','w'))
for row in reader:
    reader = re.sub(r'\+','z',reader)

Which is giving me the following error:

Script error: Traceback (most recent call last):
  File "ffrk_inventory_tracker_v1.6.py", line 22, in response
    getRelics(data['equipments'], 'ffrk_inventory_relics')
  File "ffrk_inventory_tracker_v1.6.py", line 72, in getRelics
    reader = re.sub(r'\+','z',reader)
  File "c:\users\baconcatbug\appdata\local\programs\python\python36\lib\re.py",
line 191, in sub
    return _compile(pattern, flags).sub(repl, string, count)
TypeError: expected string or bytes-like object

After googling to not much luck, I would like to ask the community here how to open the csv file correctly so I can use re.sub on it and then write out the altered csv file back to the same filename.

Why are you passing reader to re.sub? Pass row instead. — Moses Koledoye
– Moses Koledoye, Commented Oct 30, 2017 at 13:42
@MosesKoledoye row is a list and not a proper arg for re.sub either. — user2390182
– user2390182, Commented Oct 30, 2017 at 13:45

Ajax1234 · Accepted Answer · 2017-10-30 14:11:56Z

1

csv.reader(open('ffrk_inventory_relics.csv', 'r')) is creating a list of lists, and when you iterate over it and pass each value to re.sub, you are passing a list, not a string. Try this:

import re
import csv
final_data = [[re.sub('\+', 'z', b) for b in i] for i in csv.reader(open('ffrk_inventory_relics.csv', 'r'))]
write = csv.writer(open('ffrk_inventory_relics.csv'))
write.writerows(final_data)

edited Oct 30, 2017 at 14:11

answered Oct 30, 2017 at 13:44

Ajax1234

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1 Comment

BaconCatBug Over a year ago

And how do I write final_data to the csv file?

zipa · Accepted Answer · 2017-10-30 13:49:11Z

0

If you don't need csv you can use replace with regular open:

with open('ffrk_inventory_relics.csv', 'r') as reader, open('outfile.csv','w') as writer:
    for row in reader:
        writer.write(row.replace('+','z'))

answered Oct 30, 2017 at 13:49

zipa

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5 Comments

BaconCatBug Over a year ago

The + and z were just test strings to replace, the final replacement is a big regex argument

zipa Over a year ago

Sure you can change that row into desired regex in sense row = re.sub('\+', 'z', row)

BaconCatBug Over a year ago

The following code is working, but how do I make outfile.csv replace ffrk_inventory_relics.csv? (No idea why the formatting is mangled I don't know how to express the below in a code block) with open('ffrk_inventory_relics.csv', 'r') as reader, open('outfile.csv','w') as writer: for row in reader: row = re.sub('(\+*,[^,]*,[^,]*,[^,]*,\ 0)', ' (Core)\\g<1>', row) writer.write(row)

zipa Over a year ago

Have you considered using pandas? I think it would solve your problem.#

BaconCatBug Over a year ago

I have no idea what pandas is or how it would help.

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