how to convert a comma delimited file to tab delimited file using python

> for line in open("testdatasent.csv"):
> line.replace (',', '      ')

If the file were reasonably small then the code could be enhanced to

f = open('testdatasent.csv')
content = f.read()
new_content = content.replace(',', '\t')
f.close()

and the new_content could be used directly or could be written to another file. However, data stored in csv files are not that simple. Generally, the csv format must be capable to capture also the string values with commas inside. The strings are quoted for that purpose. The comma inside a string is not the separator. Parser of the csv files is therefore not as easy as splitting on commas.

You should have a look at the Python standard module csv (see http://docs.python.org/lib/module-csv.html). See also some examples how to use it -- http://docs.python.org/lib/csv-examples.html

As said above, this would not work for csv files with commas inside strings. Otherwise, this would be fine.

But you can try the following. Save the next lines into some.csv

===================================
1,"string",2.58
2,"string B, with comma inside",15
===================================

And then save the snippet into the testCSV.py (or so)... This will generate output.txt with tab delimited values.

The principle is based on the fact that a csv.reader() class instance returns rows that take the form of lists of values (try to uncomment the print row command to visualize it on display). The list of values can be connected to a string using the join() method of the built-in string class. The separator is the string for which the join() is called. This way the command

'\t'.join(row)

joins all values using the tabulator into a single string. The \n is appended after and the resulting string is written to the output text file.

Possibly another way could be to use the csv.writer() instance with dialect='excel-tab'. I did not try, but I expect the same result.

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import csv
 
fin = open('some.csv', 'rb')  # doc says that binary mode must be used
fout = open('output.txt', 'w')
 
reader = csv.reader(fin)
 
for row in reader:
   ##print row
   fout.write('\t'.join(row) + '\n')
 
fin.close()
fout.close()

I tried it with the writer. The output file also must be opened in binary mode. See the snippet.

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import csv
 
fin = open('some.csv', 'rb')     # doc says that binary mode must be used
fout = open('output.txt', 'wb')  # output also have to be in binary mode
 
reader = csv.reader(fin)
writer = csv.writer(fout, dialect='excel-tab')
 
for row in reader:
   writer.writerow(row)
 
fin.close()
fout.close()