Python script to get delta_T from USNO.

get_delta_t_usno.py

#! /usr/local/bin/python3.6
"""
USNO（アメリカ海軍天文台） から delta T(ΔT) を取得
: 確定データは
  [Delta T determinations](http://maia.usno.navy.mil/ser7/deltat.data)
  から、推定データは
  [Delta T predictions](http://maia.usno.navy.mil/ser7/deltat.preds)
  から取得する。

  date          name            version
  2018.06.20    mk-mode.com     1.00 新規作成

Copyright(C) 2018 mk-mode.com All Rights Reserved.
---
引数 : UTC (YYYYMMDD 形式)
       * 無指定ならシステム日時を UTC とみなす
"""
from datetime import datetime
import re
import requests
import sys
import traceback


class GetDeltaTUsno:
    USAGE = "[USAGE] ./get_delta_t_usno.py [yyyymmdd]"
    URL_D = "http://maia.usno.navy.mil/ser7/deltat.data"
    URL_P = "http://maia.usno.navy.mil/ser7/deltat.preds"
    UA = (
        "<BOT_NAME> (by Python/{}.{}.{}, "
        "Administrator: <MAIL_ADDRESS>)"
    ).format(
        sys.version_info.major,
        sys.version_info.minor,
        sys.version_info.micro
    )
    PTN_0 = re.compile(r'[\r\n]+')
    PTN_1 = re.compile(r'^\s+')
    PTN_2 = re.compile(r'\s+')
    PTN_3 = re.compile(r'[\d\.]+')
    PTN_4 = re.compile(r'\.')

    def __init__(self):
        self.__get_arg()
        self.data = []    # delta t 一覧
        self.delta_t = 0  # delta t 初期値
        self.dp = ""      # 確定／推定値区分（推定値なら "*"）

    def exec(self):
        try:
            self.__get_determination()  # 確定データ取得
            self.__get_prediction()     # 推定データ取得
            self.__get_delta_t()        # delta_t 取得
            self.__display()            # 結果出力
        except Exception as e:
            raise

    def __get_arg(self):
        """ argument getting """
        try:
            if len(sys.argv) > 1:
                ymd = sys.argv[1]
            else:
                ymd = datetime.now().strftime("%Y%m%d")
            if not(re.search(r"^\d{8}$", ymd)):
                print(self.USAGE)
                sys.exit(0)
            self.date = "{}-{}-{}".format(ymd[0:4], ymd[4:6], ymd[6:8])
        except Exception as e:
            raise

    def __get_determination(self):
        """ 確定データ取得 """
        try:
            headers = {'user-agent': self.UA}
            res = requests.get(self.URL_D, headers=headers)
            html = res.text.strip()
            for line in re.split(self.PTN_0, html):
                line = re.sub(self.PTN_1, "", line)
                items = re.split(self.PTN_2, re.sub(self.PTN_1, "", line))
                date = "{:04d}-{:02d}-{:02d}".format(
                    int(items[0]), int(items[1]), int(items[2])
                )
                self.date_max = date
                self.data.append([date, float(items[-1]), "D"])
        except Exception as e:
            raise

    def __get_prediction(self):
        """ 推定データ取得 """
        try:
            headers = {'user-agent': self.UA}
            res = requests.get(self.URL_P, headers=headers)
            html = res.text.strip()
            for line in re.split(self.PTN_0, html):
                line = re.sub(self.PTN_1, "", line)
                items = re.split(self.PTN_2, re.sub(self.PTN_1, "", line))
                if not(re.match(self.PTN_3, items[0])):
                    continue
                year, year_frac = re.split(self.PTN_4, items[0])
                year = int(year)
                if year_frac == "00":
                    month = 1
                elif year_frac == "25":
                    month = 4
                elif year_frac == "50":
                    month = 7
                elif year_frac == "75":
                    month = 10
                date = "{:04d}-{:02d}-01".format(year, month)
                if date <= self.date_max:
                    continue
                self.data.append([date, float(items[1]), "P"])
        except Exception as e:
            raise

    def __get_delta_t(self):
        """ delta t 取得 """
        try:
            for i, d in enumerate(reversed(self.data)):
                if d[0] <= self.date:
                    if i == 0:
                        break
                    self.delta_t = d[1]
                    if d[2] == "P":
                        self.dp = "*"
                    break
        except Exception as e:
            raise

    def __display(self):
        """ 結果出力 """
        try:
            print("[{}] delta_T = {} sec. {}".format(
                self.date, self.delta_t, self.dp)
            )
        except Exception as e:
            raise


if __name__ == '__main__':
    try:
        obj = GetDeltaTUsno()
        obj.exec()
    except Exception as e:
        traceback.print_exc()
        sys.exit(1)