Question

我不明白为什么它适用于不同的场景，但不适用于此场景。基本上，一些绅士帮助我HERE改进我的代码以刮除天气，这完美地运作。然后我尝试做同样的事情来刮取跨度标记<span class="text-large2" data-currency-value="">$196.01</span>中的ETH值。所以，我在代码中遵循相同的技术，替换了字段，并希望它能够工作。

代码在这里：

import requests
from BeautifulSoup import BeautifulSoup
import time

url = 'https://coinmarketcap.com/currencies/litecoin/'

def ltc():
    while (True):
        response = requests.get(url)
        soup = BeautifulSoup(response.content)
        price_now = int(soup.find("div", {"class": "col-xs-6 col-sm-8 col-md-4 text-left"}).find(
        "span", {"class": "text-large2"}).getText())
        print(u"LTC price is: {}{}".format(price_now))
        # if less than 150
        if 150 > price_now:
            print('Price is Low')
        # if more than 200
        elif 200 < price_now:
            print('Price is high')

if __name__ == "__main__":
    ltc()

输出如下：

Traceback (most recent call last):
  File "test2.py", line 24, in <module>
    ltc()
  File "test2.py", line 13, in ltc
    "span", {"class": "text-large2"}).getText())
ValueError: invalid literal for int() with base 10: '196.01'

然后，我终于以这种方式尝试了;但从这里我得到误报，但没有错误。它打印任何想要的东西

import requests
from bs4 import BeautifulSoup
import time

url = 'https://coinmarketcap.com/currencies/litecoin/'

def liteCoin():
    while (True):
        response = requests.get(url)
        html = response.text
        soup = BeautifulSoup(html, 'html.parser')
        value = soup.find('span', {'class': 'text-large2'})
        print(''.join(value.stripped_strings))
        if 150 > value:         # if less than 150
            print('Price is Low!')
        elif 200 < value:       # if more than 200
            print('Price is High')
        else:
            print('N/A')
        time.sleep(5)

if __name__ == "__main__":
    liteCoin()

问题是ETH的值在$内有span tag符号吗？而且，这样程序不知道如何处理字符串？

Answer 1

首先，让我们简化您的示例程序：

>>> int('196.01')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '196.01'

无法将字符串'196.01'转换为整数。

试试这个：

>>> int(float('196.01'))
196

从简单回到复杂，我们可以这样做：

#UNTESTED
price_now = int(float(soup.find("div", {"class": "col-xs-6 col-sm-8 col-md-4 text-left"}).find(
    "span", {"class": "text-large2"}).getText()))

Answer 2

你需要理解Python中的类型，你得到的浮点数不是int，你需要将float转换为字符串来打印它。所以需要进行两项更改。

    price_now = float(soup.find("div", {"class": "col-xs-6 col-sm-8 col-md-4 text-left"}).find("span", {"class": "text-large2"}).getText())
    print(u"LTC price is: {}".format(str(price_now)))

输出：

LTC price is: 195.44
LTC price is: 195.44

ValueError：基数为10的int（）的无效文字：'196.41'

2 个答案: