Let's take a tab-delimited file and replace its first column with nine spaces. Let's do this ... to all tab-delimited files.

replace_first_column_with_nine_spaces.py

#!/usr/bin/env python3

import sys

# Check command line arg
if len(sys.argv) != 2:
    sys.stderr.write("usage: replace_first_column_with_nine_spaces.py <input.tsv>\n")
    sys.exit()

# Open file
with open(sys.argv[1], 'r') as infile:
    for line in infile:
        fields = line.split("\t")
        fields[0] = "         " # 9 spaces y'all
        sys.stdout.write("\t".join(fields))