Python 3:

The official csv documentation recommends opening the file with newline='' on all platforms to disable universal newlines translation:

with open('output.csv', 'w', newline='', encoding='utf-8') as f:
    writer = csv.writer(f)
    ...

The CSV writer terminates each line with the lineterminator of the dialect, which is '\r\n' for the default excel dialect on all platforms because that's what RFC 4180 recommends.

Python 2:

On Windows, always open your files in binary mode ("rb" or "wb"), before passing them to csv.reader or csv.writer.

Although the file is a text file, CSV is regarded a binary format by the libraries involved, with \r\n separating records. If that separator is written in text mode, the Python runtime replaces the \n with \r\n, hence the \r\r\n observed in the file.

See this previous answer.

The strip() method removes whitespace, including newlines.

fileout.writerow(line.strip())

The csv.writer module directly controls line endings and writes \r\n into the file directly. In Python 3 the file must be opened in untranslated text mode with the parameters 'w', newline='' (empty string) or it will write \r\r\n on Windows, where the default text mode will translate each \n into \r\n.

#!python3
with open('/pythonwork/thefile_subset11.csv', 'w', newline='') as outfile:
    writer = csv.writer(outfile)

If using the Path module:

from pathlib import Path
import csv

with Path('/pythonwork/thefile_subset11.csv').open('w', newline='') as outfile:
    writer = csv.writer(outfile)

If using the StringIO module to build an in-memory result, the result string will contain the translated line terminator:

from io import StringIO
import csv

s = StringIO()
writer = csv.writer(s)
writer.writerow([1,2,3])
print(repr(s.getvalue()))  # '1,2,3\r\n'   (Windows result)

If writing that string to a file later, remember to use newline='':

# built-in open()
with open('/pythonwork/thefile_subset11.csv', 'w', newline='') as f:
    f.write(s.getvalue())

# Path's open()
with Path('/pythonwork/thefile_subset11.csv').open('w', newline='') as f:
    f.write(s.getvalue())

# Path's write_text() added the newline parameter to Python 3.10.
Path('/pythonwork/thefile_subset11.csv').write_text(s.getvalue(), newline='')

In Python 2, use binary mode to open outfile with mode 'wb' instead of 'w' to prevent Windows newline translation. Python 2 also has problems with Unicode and requires other workarounds to write non-ASCII text. See the Python 2 link below and the UnicodeReader and UnicodeWriter examples at the end of the page if you have to deal with writing Unicode strings to CSVs on Python 2, or look into the 3rd party unicodecsv module:

#!python2
with open('/pythonwork/thefile_subset11.csv', 'wb') as outfile:
    writer = csv.writer(outfile)

Documentation Links

• https://docs.python.org/3/library/csv.html#csv.writer
• https://docs.python.org/2/library/csv.html#csv.writer

Use file.seek to move file pointer before the last \r\n, then use file.truncate.

import os
import csv

with open('eggs.csv', 'wb') as csvfile:
    spamwriter = csv.writer(csvfile, delimiter=' ',
                            quotechar='|', quoting=csv.QUOTE_MINIMAL)
    spamwriter.writerow(['Spam'] * 5 + ['Baked Beans'])
    spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])
    csvfile.seek(-2, os.SEEK_END) # <---- 2 : len('\r\n')
    csvfile.truncate()            # <----

NOTE: You should change -2 if you use different lineterminator. I used -2 because \r\n is default lineterminator.

Recommended implementation per Python3 Documentation.

with open('records.csv','w', newline='') as csvfile:
    #creating  a csv writer object
    csvwriter = csv.writer(csvfile)
    #writing the fields
    csvwriter.writerow(fields)
    # writing the data rows
    csvwriter.writerows(rows)

https://docs.python.org/3/library/csv.html#csv.writer

This problem occurs only with Python on Windows.

In Python v3, you need to add newline='' in the open call per:

Python 3.3 CSV.Writer writes extra blank rows

On Python v2, you need to open the file as binary with "b" in your open() call before passing to csv

Changing the line

with open('stocks2.csv','w') as f:

to:

with open('stocks2.csv','wb') as f:

will fix the problem

More info about the issue here:

CSV in Python adding an extra carriage return, on Windows