处理理解列表中的 'NoneType' object is not iterable' 错误

Question

I'm trying to scrape quantity from a site using this code:

qty = [qty.text.strip() for qty in soup.find("span", attrs={"class":"item-quantity"})]

but the value is not always present so I'm getting this error:

'NoneType' object is not iterable

is there a way to insert an if and else statement in a list of comprehension? So that when the quantity is not present in the list the value "1" is saved. I've tried

qty = [qty.text.strip() for qty in soup.find("span", attrs={"class":"item-quantity"})if x is not None else x="1"]

But I'm getting an error of invalid syntax

Answer 1

I highly recommend using a for loop here, but here's one way to do this

qty = [qty.text.strip() for qty in soup.find("span", attrs={"class":"item-quantity"}) or []]

Since None is Falsy, it evaluates the expression after or

print(None or []) # []
print([1,2,3] or []) # [1,2,3]

Answer 2

Try:

qt = [qty.text.strip() for qty in soup.find_all("span", attrs={"class":"item-quantity"}) if qty  else "1"]

Answer 3

List comprehensions have the ability to use ternary expressions like this:

qty = [qty.text.strip() if qty else "1" for qty in soup.find("span", attrs={"class":"item-quantity"})]

It is also possible to use a normal loop and add try/except instead of an if/else .