import csv


def read_primes(file_name):
    """Read a list of prime numbers from a csv file
 
    Args:
        file_name (str): file name of a csv file
 
    Raises:
        IOError: if file is not able to be read
 
    Examples:
        >>> l = read_primes('output.csv')
 
    """
    with open(file_name, newline='') as csvfile:
        reader = csv.reader(csvfile, delimiter=',')
        for row in reader:
            prime_list = []
            for field in row:
                prime_list.append(int(field))
            return prime_list