python - 如何创建在偶尔设置非类型的功能输入中发生的 NoneType 错误解决方法

Question

我有一种情况，即输入代码的数据集会产生 NoneType 错误。在尝试了几个变体来解决错误后，我不确定如何修改代码来做到这一点。这是追溯。

Traceback (most recent call last):
  File "A:\anoth\test.py", line 64, in <module>
    pretty_print(master)
  File "A:\anoth\\test.py", line 53, in pretty_print
    categories = find_elms(soup, 'div', {'id': 'categories'})
  File "A:\anoth\\test.py", line 37, in find_elms
    for region in regions:
TypeError: 'NoneType' object is not iterable

当 NoneType 数据进入代码时，下面的 if-then 循环没有起作用。

regions = soup.find(tag, attribute)
print('this ' + str(regions))
for region in regions: #this works for portions of the data set
    if [elm.text for elm in regions.find_all('a')] is None:
        return [] 
    else:
        return [elm.text for elm in regions.find_all('a')]

return []

有什么想法吗？

Answer 1

你的代码不起作用的原因是因为 regions 在某些时候是 None，而你试图在你的 for 循环中迭代 None，因此错误'NoneType' 对象不可迭代

regions = soup.find(tag, attribute)  #<------ this is returning None
print('this ' + str(regions))
for region in regions: #<-- you can't take a region in regions, when regions is None
    if [elm.text for elm in regions.find_all('a')] is None:
        return [] 
    else:
        return [elm.text for elm in regions.find_all('a')]

return []

你可以在里面添加一个try except:

try:
    regions = soup.find(tag, attribute)
    print('this ' + str(regions))
    for region in regions: #this works for portions of the data set
        if [elm.text for elm in regions.find_all('a')] == []:
            return [] 
        else:
            return [elm.text for elm in regions.find_all('a')]

except:
    print ('regions is NoneType object')
    return []