Checking if a variable or parameter is None should only be done when you expect that it can be None. Doing so when the
variable is always None or never None is confusing at best. At worse, there is a bug and the variable is not updated properly.
This rule raises an issue when expressions X is None, X is not None, X == None or X != None are
constant, i.e. X is always None or never None.
Noncompliant Code Example
mynone = None
result = mynone is None: # Noncompliant. Always True.
if mynone == None: # Noncompliant. Always True.
pass
if mynone is not None: # Noncompliant. Always False.
pass
if mynone == None: # Noncompliant. Always False.
pass
myint = 42
result = myint is None: # Noncompliant. Always False.
if myint == None: # Noncompliant. Always False.
pass
if myint is not None: # Noncompliant. Always True.
pass
if myint == None: # Noncompliant. Always True.
pass
See
