This script will process the json dump from Google Takeout to extract all messages sent between two people. Before extracting the conversation you need to know the conversation_id.

hangout-filter.py

# example:
# python hangout-filter.py Hangouts.json Ugw3axd-nDFKCvFsDi94AaABAQ | sort | tr '\n' ' ' > words.txt

# !/usr/bin/env python

import json
import argparse
import dateutil.parser
import re

parser = argparse.ArgumentParser(
	description='Print conversations in readable format.')
parser.add_argument('filename')
parser.add_argument('conversation_id')
args = parser.parse_args()

data = json.load(open(args.filename))

states = data['conversation_state']
for state in states:
	conversation_state = state['conversation_state']
	if 'event' in conversation_state:
		conversations = conversation_state['event']
		for conversation in conversations:
			if 'chat_message' in conversation:
					message_content = conversation['chat_message']['message_content']
					if 'segment' in message_content:
						segment = message_content['segment']
						for line in segment:
							conversation_id = conversation['conversation_id']['id']
							if conversation_id == args.conversation_id:
								timestamp = conversation['timestamp']
								user_id = conversation['sender_id']['gaia_id']
								# out = user_id + ' @ ' + timestamp + ': ' + line['text']
								# print(out.encode('ascii', 'ignore').replace('\n', ''))
								out = line['text']
								out = out.encode('ascii', 'ignore')
								out = re.sub('\s+', '\n', out)
								print(out)