Write a float array to a CSV file

Question

I have a float array (created by: array('f')) and I want to write its contents as a 1-column CSV file, that is, each element of the array will take one line of the resulting file.

from array import array

my_array = array('f')
with open(filename, 'w') as output:
    my_array = populate_method()
    writer = csv.writer(output)
    print(my_array)  # verifying that the data exist
    writer.writerows(my_array.tolist())

I get this error at the latest line: _csv.Error: sequence expected.
What is wrong? Isn't the list a sequence?

Joran Beasley · Accepted Answer · 2015-09-11 00:27:06Z

0

why ... you can just write it

with open("outfile","wb") as f:
     f.write("\n".join(str(x) for x in my_list))

the problem with your original code is that writerows expects a 2d list and you are just giving it a one dimensional list, therfor alternatively you can convert your 1d list into a 1column 2d list with

my_list_i_can_use_with_writerows = zip(*[myList])

answered Sep 11, 2015 at 0:27

Joran Beasley

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1 Comment

Chris Over a year ago

Writing it directly was my first attempt, but didn't came up with the "\n".join syntax and so all the elements were in one line. Some follow-up questions: 1. Why does write_rows expect a 2D list? 2. Could you elaborate on the syntax of zip(*[myList]) ?

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