Thank you all for your answers. As a beginner, my main problem was the occurrence of a blank line upon .split(',') which I have now understood conceptually. So my first useful program in python is here:
# this script converts a .fastq file in to .fasta format
import sys
# Usage statement:
print('\nUsage: fq2fasta.py input-file output-file\n=========================================\n\n')
# define a function for fasta formating
def format_fasta(name, sequence):
fasta_string = '>' + name + "\n" + sequence + '\n'
return fasta_string
# open the file for reading
data = open(sys.argv[1])
# open the file for writing
fasta = open(sys.argv[2], 'wt')
# feed all fastq records in to a list
fq_records = data.read().replace('@', ',@').split(',')
# iterate through list objects
for item in fq_records[1:]: # this is to avoid the first line which is created as blank by .split() function
line = item.replace('\n', '\t').split('\t')
name = line[0]
sequence = line[1]
fasta.write(format_fasta(name, sequence))
fasta.close()
Other things suggested in the answers would be more clear to me as I learn more.
Thanks again.