Build a mortgage rates bot for X
the weekly rate, housing news, payment math

import os, csv, io, pathlib, requests

OT = {"Authorization": f"Bearer {os.environ['OPENTWEET_API_KEY']}"}
LAST = pathlib.Path("last_pmms_date.txt")

resp = requests.get(
    "https://fred.stlouisfed.org/graph/fredgraph.csv",
    params={"id": "MORTGAGE30US,MORTGAGE15US"},
    headers={"User-Agent": "Mozilla/5.0 (mortgage-rate-bot; you@example.com)"},
    timeout=60,
)
rows = [r for r in csv.DictReader(io.StringIO(resp.text)) if r["MORTGAGE30US"] not in ("", ".")]
week, prev, year_ago = rows[-1], rows[-2], rows[-53]

if LAST.exists() and LAST.read_text().strip() == week["observation_date"]:
    raise SystemExit("no new survey yet")

def move(now, before):
    d = float(now) - float(before)
    return "unchanged" if abs(d) < 0.005 else f"{'up' if d > 0 else 'down'} {abs(d):.2f}"

text = (
    f"30-year fixed mortgage rate: {float(week['MORTGAGE30US']):.2f}% "
    f"({move(week['MORTGAGE30US'], prev['MORTGAGE30US'])} from last week)\n"
    f"15-year fixed: {float(week['MORTGAGE15US']):.2f}% "
    f"({move(week['MORTGAGE15US'], prev['MORTGAGE15US'])})\n\n"
    f"A year ago the 30-year was {float(year_ago['MORTGAGE30US']):.2f}%.\n"
    f"Source: Freddie Mac PMMS, week of {week['observation_date']}"
)
requests.post("https://opentweet.io/api/v1/posts", headers=OT,
              json={"text": text, "publish_now": True}).raise_for_status()
LAST.write_text(week["observation_date"])

30-year fixed mortgage rate: 7.18% (down 0.06 from last week)
15-year fixed: 6.57% (down 0.03)

A year ago the 30-year was 6.22%.
Source: Freddie Mac PMMS, week of 2026-11-05

# Every hour from 8:00 to 18:00 New York time on Wednesdays and Thursdays
CRON_TZ=America/New_York
0 8-18 * * 3,4  cd /opt/mortgage-bot && python3 post_rate.py