NoneType is the type for the None object, which is an object that indicates no value. None is the return value of functions that “don’t return anything”. It is also a common default return value for functions that search for something and may or may not find it; for example, it’s returned by re.search when the regex doesn’t match, or dict.get when the key has …
So how can I question a variable that is a NoneType? Use is operator, like this Why this works? Since None is the sole singleton object of NoneType in Python, we can use is operator to check if a variable has None in it or not. Quoting from is docs, The operators is and is not test for object identity: x is y is true if and only if x and y are the same object. x is …
is the Pythonic idiom for testing that a variable is not set to None. This idiom has particular uses in the case of declaring keyword functions with default parameters. is tests identity in Python. Because there is one and only one instance of None present in a running Python script/program, is is the optimal test for this. As Johnsyweb points out, this is discussed …
It means the value of data is None.
NoneType means that instead of an instance of whatever Class or Object you think you’re working with, you’ve actually got None. That usually means that an assignment or function call up above failed or returned an unexpected result.
There’s no performance difference, as they compile to the same bytecode: Stylistically, I try to avoid not x is y, a human reader might misunderstand it as (not x) is y. If I write x is not y then there is no ambiguity.
You want to pass the function object hi to your loop() function, not the result of a call to hi() (which is None since hi() doesn’t return anything). So try this: Perhaps this will help you understand better:
It means the value of data is None.
It means the value of data is None.