Testing for Membership

00:00 Now that you know how and where to use the not operator, let’s look at some best practices for using it in Python, starting with membership.

00:12 Consider you want to determine if an item is in a particular collection or not. In Python, you use the in operator to do that. So if you create a list of numbers, you can see that 3 is in it, and 5 is not.

00:41 If you want to return True when something is not in a collection and False when it is, use the not operator in this way,

00:59 "c" is in that list, so to ask if it is not in that list will return False. Note that it’s preferred in Python to type "c" not in ["a", "b", "c"] instead of not "c" in ["a", "b", "c"].

01:20 Here’s another example of membership based on something you saw before. Recall using and to see if a number was in a particular range. But Python has a range() function to generate the collection of integers in a range. So you can use the in operator to test for that.

01:39 So now, if you want to test if a number is outside that range, you can use the not operator. Using values you’ve seen before, you can now check that 30 is in that range

02:04 and not outside that range, but that 50 is outside that range.

02:26 Next, you’ll see how the not operator can be used when checking object identity.