Extract Hosts from HAR

har_hosts.py

#!/usr/bin/env python3
import json
import sys

try:
    file_path = sys.argv[1]
except IndexError:
    sys.stderr.write(f"Usage: {sys.argv[0]} <file_path>\n")
    sys.exit(1)

with open(file_path) as f:
    doc = json.load(f)

print(set([ header['value']
      for entry in doc['log']['entries']
      for header in entry['request']['headers']
      if header['name'] == 'Host'
]))