Implicit conversion to boolean in if and while statements

[Andrew Berg]

On 7/15/2012 9:38 PM, Steven D'Aprano wrote:
>> I would expect None to mean "doesn't exist" or "unknown" or
>> something like that - e.g., a value of 0 means 0 jelly beans in the jar
>> and None means there isn't a jar.
> 
> How you interpret some_variable = None depends on what some_variable 
> represents. If some_variable represents "number of jelly beans in a jar", 
> then that should be 0 if there is no jar.
What is None supposed to mean then, and what should I do when I have to
make a distinction between "doesn't exist" and "empty"? Sure, if I need
to count the total number of jelly beans in all my stores, the
distinction is meaningless, but if I need to find out which stores sell
jelly beans so I know which stores need to be restocked, the distinction
is quite important.
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