how to convert all dot decimal marker in csv files to comma using python?

Question

I have multiple csv files.

in these files, "dot" used as a decimal marker.

I would like to change all dots to commas and then combine all csv files into one csv file. How can I do this in python?

Possible duplicate of: https://stackoverflow.com/questions/6630170/python-parse-csv-file-replace-commas-with-colons & https://stackoverflow.com/questions/45256104/python-csv-change-separator — Wilmar van Ommeren, Oct 11 '18 at 13:07
@Qiu That question changes the delimitter while op here asks to change decimal marker — Florian H, Oct 11 '18 at 13:38

score 0 · Answer 1 · edited Oct 11 '18 at 13:17

0

You could parse csv row per row and then use replace() function on values where you want to replace .

Then, after this transformation, you write this row on a new CSV file.

edited Oct 11 '18 at 13:17

Jan Černý

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answered Oct 11 '18 at 12:59

Dazounet

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Florian H · Answer 2 · 2018-10-11T13:58:15.183

0

As @Dazounet mentioned you can read file by file and line by line and replace "manually"

from os import listdir
from os.path import isfile, join

mypath = "pathToFolder/"
files = [f for f in listdir(mypath) if isfile(join(mypath, f))]

with open(mypath + "target.csv", 'a') as outfile:
    for file in files:
        with open(mypath+file, "r") as infile:
             next(infile)
             for line in infile:
                    line = line.replace("." , ",")
                    outfile.write(line)

The code is not tested

edited Oct 11 '18 at 13:58

answered Oct 11 '18 at 13:04

Florian H

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thanks! this is the error that i got: files = [f for f in listdir(mypath) if isfile(join(mypath, f))] NameError: name 'listdir' is not defined – Anahita Kp Oct 11 '18 at 13:28
it destroyed the structure of the csv files. it added all the headers – Anahita Kp Oct 11 '18 at 13:52
just skip the first line with next(infile) to ignore the headers. i add it to the answer – Florian H Oct 11 '18 at 13:57
now it removes all headers and add more columns! is it possible to keep the first file with its header and append other fils without headers? – Anahita Kp Oct 11 '18 at 14:14
yes you could do that if you want. you might consider using pandas as Daren Thomas suggested. – Florian H Oct 11 '18 at 14:18

Daren Thomas · Answer 3 · 2018-10-11T14:10:58.447

Using pandas makes writing out the numbers with commas trivial:

read in the csv file (df = pd.read_csv('path/to/file.csv'))
write out the csv file (df.to_csv('path/to/file.csv', decimal=','))

Note, this will add quotes to all your numbers, since the separator normally used is ,. You can change that with the sep=';' argument for instance.

I'll leave finding all the files to join as an exercise for the reader (see other answers here).

As for combining all the files into one file:

df = pd.concat([pd.read_csv(fname) for fname in files_to_convert])

how to convert all dot decimal marker in csv files to comma using python?

3 Answers3