如何修复位置参数自我错误

Question

当我尝试运行我的代码时，我遇到了一个错误，即我错过了1个必需的位置参数：'self'。我不知道如何解决这个问题。

import urllib.request
import re
from lxml import html

class test:           
    def start(self) :

        url = 'http://money.cnn.com/data/dow30/'

        global Ticker

        increase = 0
        while increase < 30:

            req = urllib.request.Request(url)
            resp = urllib.request.urlopen(req)
            respData = resp.read()

            html_data = html.fromstring(respData)

            Ticker = html_data.xpath('//a[@class="wsod_symbol"]/text()')[increase]

            print(Ticker)

            return Ticker              
            increase += 1
    start()

    def earnings(self):

        url = 'https://www.google.com/finance?q=NYSE:' + Ticker

        req = urllib.request.Request(url)
        resp = urllib.request.urlopen(req)
        respData = resp.read()

        html_data = html.fromstring(respData)

        eps = html_data.xpath('//td[@class="val"]/text()')[7]

        blah = re.findall(r'\d+\.\d+', eps)

        print(float(blah[0]))