Is there a simple command for outputting a tab delimited columns?
I have no idea what do you want to do with fasta files reformatted like this, but I think something like this should do the job (untested):
from Bio import SeqIO 
import sys 

for olig_fasta in SeqIO.parse(sys.argv[1], &quot;fasta&quot;):

  name = olig_fasta.name
  seq = str(olig_fasta.seq)
  seq_len = str(len(olig_fasta.seq))

  print(&quot;\t&quot;.join([name, seq_len, seq]))