Writing to a CSV File from Array

Question

I am trying to use writer.writerow to present data from an array to an csv file. I have an array sum_balance and apparently I need to convert it into a numpy array before I can use the writer.writerow function. Heres my code:

numpy_arr = array(sum_balance)
with open("output.csv", "wb") as csv_file:
    writer = csv.writer(csv_file, delimiter=',')
    for element in numpy_arr:
        writer.writerow(element)
csv_file.close()

But I still get the error: writer.writerow(element)_csv.Error: iterable expected, not numpy.float64

Ben G. · Accepted Answer · 2017-06-12 21:29:18Z

2

The numpy iterator seems to be iterating over elements, not rows, which is why you're getting an error. However, there's an even simpler way to achieve what you're trying to do: numpy has a routine savetxt that can write an ndarray to a csv file:

output_array = np.array(my_data)
np.savetxt("my_output_file.csv", output_array, delimiter=",")

answered Jun 12, 2017 at 21:29

Ben G.

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2 Comments

anderish Over a year ago

It prints it row by row, is it possible to print it column by column?

Ben G. Over a year ago

Yes. Any numpy.ndarray can be transposed with array_name.T. So to write with columns as rows you just need to do np.savetext("output_file_name", array_name.T, delimiter=',').

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