The savetxt() function admits several parameters, which are useful when we want to output the array in a format that is compatible with a specific application. In this recipe, we show you how to store a NumPy array in CSV format. Comma-separated values (CSV) are used to store tabular data in a text file. Each row of the table is stored in a line of text and elements in each row are separated by a comma. The following code illustrates how to save an array in CSV format:

m, n = 10, 5
x = np.random.rand(m, n)
columns = ','.join(['Column {}'.format(str(i+1)) for i in range(n)])
np.savetxt('array_x.csv', x, fmt='%10.8f', 
           delimiter=',', header=columns, comments='')

With this code, we first generate a 10 x 5 array x with random data. Next, we define a columns string containing the table headings, separated by commas. Finally, we save the array to the array_x.csv file. The options used in the call to savetxt() are described as follows:

• fmt='%10.8f' specifies that each array element should be formatted as a floating-point value in a field with a width of 10 and a precision of 8 decimals.
• delimiter=',' sets the field separator to be a comma.
• header=columns directs save_text() to output the columns string at the top of the file. This effectively sets the headings for each column in the CSV file.
• comments='' is necessary because save_text(), by default, prepends a # to the headers line. This options tells us that an empty string should be prepended instead.

The output file, array_x.csv, can be opened with any spreadsheet software.