Python如何添加异常？ [英] Python how to add exception?

问题描述

@martineau我已经更新了我的代码，这是你的意思吗？我如何处理KeyError而不是NameError？

@martineau I have updated my codes, is this what you meant ? How do i handle KeyError instead of NameError ?

url = "http://app2.nea.gov.sg/anti-pollution-radiation-protection/air-pollution/psi/psi-readings-over-the-last-24-hours"
web_soup = soup(urllib2.urlopen(url))

table = web_soup.find(name="div", attrs={'class': 'c1'}).find_all(name="div")[4].find_all('table')[0]

data = {}
cur_time = datetime.datetime.strptime("12AM", "%I%p")
for tr_index, tr in enumerate(table.find_all('tr')):
    if 'Time' in tr.text:
        continue
    for td_index, td in enumerate(tr.find_all('td')):
        if not td_index:
            continue
        data[cur_time] = td.text.strip()

        if td.find('strong'):
            bold_time = cur_time
            data[bold_time] = '20'
        cur_time += datetime.timedelta(hours=1)

        default_value = '20' # whatever you want it to be

    try:
        bold = data[bold_time]
    except NameError:

        bold_time = beforebold = beforebeforebold = default_value
    # might want to set "bold" to something, too, if needed
    else:   
        beforebold = data.get(bold_time - datetime.timedelta(hours=1)) 
        beforebeforebold =  data.get(bold_time - datetime.timedelta(hours=2))

这是我打印数据进行计算的地方。

This is where I print my data to do calculation.

print bold
print beforebold
print beforebeforebold

推荐答案

p>您需要添加一些设置数据[bold_time] ：

You need to add something to set data[bold_time]:

    if td.find('strong'):
        bold_time = cur_time
        data[bold_time] = ????? # whatever it should be
    cur_time += datetime.timedelta(hours=1)

应该避免 NameError 和 KeyError 异常，只要单词 strong 被找到。你仍然可能想要防御性地进行编码，并且优雅地处理其中的一个或两个。这是什么例外，意在做什么，处理不应该发生的特殊情况...

This should avoid both the NameError and KeyError exceptions as long as the word strong is found. You still might want to code defensively and handle one or both of them gracefully. That what exception where meant to do, handle those exceptional cases that shouldn't happen...

这篇关于Python如何添加异常？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！