creating a tab delimited file
You can use a list and insert() to add an element in a specific order, then expand the list with *. Or you can use join().
from Bio import SeqIO
import sys

for hello_fasta in SeqIO.parse(sys.argv[1], &quot;fasta&quot;):
  sequences = []
  sequences.insert(0, hello_fasta.description)
  sequences.insert(1, len(hello_fasta.seq))
  sequences.insert(2, hello_fasta.seq)
  # option 1
  print(*sequences, sep='\t')
  # option 2
  print('\t'.join(map(str, sequences)))