Python爬虫获取中国银行汇率数据

# coding:utf-8

import requests
import time
from lxml import etree
import pymysql
import logging
from decimal import Decimal
from logging import handlers
from DBUtils.PooledDB import PooledDB

dbhost = '192.168.0.112'
dbname = 'tem_scms'
user = 'root'
password = 'tsc987'
pool = PooledDB(creator=pymysql,
                maxconnections=50,
                mincached=2,
                maxcached=2,
                blocking=True,
                ping=0,
                host=dbhost,
                user=user,
                passwd=password,
                database=dbname,
                port=3306,
                charset='utf8')

headers = {'Use-Agent':'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36',
           'Connection':'close'}
currency_list = ['美元','港币','欧元','日元','英镑','加拿大元']

class Logger(object):
    level_relations = {
        'debug':logging.DEBUG,
        'info':logging.INFO,
        'warning':logging.WARNING,
        'error':logging.ERROR,
        'crit':logging.CRITICAL
    }#日志级别关系映射

    def __init__(self,filename,level='info',when='D',backCount=3,fmt='%(asctime)s - %(pathname)s[line:%(lineno)d] - %(levelname)s: %(message)s'):
        self.logger = logging.getLogger(filename)
        format_str = logging.Formatter(fmt)#设置日志格式
        self.logger.setLevel(self.level_relations.get(level))#设置日志级别
        th = handlers.TimedRotatingFileHandler(filename=filename,when=when,interval=7,backupCount=backCount,encoding='utf-8')#往文件里写入#指定间隔时间自动生成文件的处理器
        #实例化TimedRotatingFileHandler
        #interval是时间间隔，backupCount是备份文件的个数，如果超过这个个数，就会自动删除，when是间隔的时间单位，单位有以下几种：
        # S 秒
        # M 分
        # H 小时、
        # D 天、
        # W 每星期（interval==0时代表星期一）
        # midnight 每天凌晨
        th.setFormatter(format_str)#设置文件里写入的格式
        self.logger.addHandler(th) #把对象加到logger里

def getInterval(now):