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I have a method that sometimes returns a NoneType value. So how can I question a variable that is a NoneType? I need to use if method, for example
if not new: new = '#' I know that is the wrong way and I hope you understand what I meant.
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To check whether a variable is None or not, use the is operator in Python. With the is operator, use the syntax object is None to return True if the object has the type NoneType and False otherwise.
Use the is not operator to check if a variable is not None in Python, e.g. if my_var is not None: . The is not operator returns True if the values on the left-hand and right-hand sides don't point to the same object (same location in memory).
The error “TypeError: 'NoneType' object is not iterable” occurs when you try to iterate over a NoneType object. Objects like list, tuple, and string are iterables, but not None. To solve this error, ensure you assign any values you want to iterate over to an iterable object.
So how can I question a variable that is a NoneType?
Use is operator, like this
if variable is None: 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
isandis nottest for object identity:x is yis true if and only ifxandyare the same object.x is not yyields the inverse truth value.
Since there can be only one instance of None, is would be the preferred way to check None.
Hear it from the horse's mouth
Quoting Python's Coding Style Guidelines - PEP-008 (jointly defined by Guido himself),
Comparisons to singletons like
Noneshould always be done withisoris not, never the equality operators.
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