import requests, sys, getopt, csv
from bs4 import BeautifulSoup

outputfile = str(sys.argv[1])

URL = 'https://www.treasury.gov/resource-center/data-chart-center/interest-rates/pages/TextView.aspx?data=billRatesYear&year=2020'
page = requests.get(URL)

soup = BeautifulSoup(page.content, 'html.parser')

results = soup.find('td')

rows = results.find_all('td', class_='text_view_data')

dates = []
values = []

for row in rows[::11]:
    dates.append(row.text)

for row in rows[1::11]:
    values.append(row.text)

with open(outputfile, 'w', newline='') as csvfile:
    fieldnames = ['date', 'rf']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

    writer.writeheader()

    for date in dates:
        index = dates.index(date)
        writer.writerow({'date': date, 'rf': values[index]})