[Tutor] List comprehension possible with condition statements?
steve at pearwood.info
Wed Mar 3 10:43:43 CET 2010
On Wed, 3 Mar 2010 07:46:39 pm Alan Gauld wrote:
> mylist = [irtem for item in aList where item != None]
Comparisons with None almost always should be one of:
item is None
item is not None
The reason is that "item is None" is ONLY ever true if the item actually
is the singleton object None (accept no substitutes!).
On the other hand, "item == None" might be true for some customer items.
So if you actually *do* want to accept substitutes, you can use ==, but
that would be an unusual thing to do, and worthy of a comment
explaining that you did mean == and it isn't a mistake.
Likewise for "item != None" versus "item is not None".
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