Writing a Python list into a single CSV column

Question

I have a list of numbers that I want to put in a single column in a .csv file. The code below writes the values across a single row. How can I change the code so that Python writes the each value on a separate row? Thanks.

        with open('returns.csv', 'wb') as f:
            writer = csv.writer(f)
            writer.writerow(daily_returns)

Solution 1

With Python3, open the file in w mode:

with open('returns.csv', 'w') as f:
    writer = csv.writer(f)
    for val in daily_returns:
        writer.writerow([val])

With Python2.6+, open the file in wb mode:

with open('returns.csv', 'wb') as f:
    writer = csv.writer(f)
    for val in daily_returns:
        writer.writerow([val])

Solution 2

Alternate solution: Assuming daily_returns is the name of the list you wish to write as a column in a CSV file, the following code should work:

with open('return.csv','w') as f:
    writer = csv.writer(f)
    writer.writerows(zip(daily_returns))

Solution 3

Just for the record:

I'm using Python 3.2 and I could only get the following to work

with open('returns','w')as f:
    writer=csv.writer(f,lineterminator='\n')
    for val in returns:
        writer.writerow([val])

Solution 4

For writing a single column, I would recommend avoiding the csv commands and just using plain python with the str.join() method:

    with open('returns.csv', 'wb') as f:
        f.write("\n".join(daily_returns))

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