learning python. learning defining functions . need help

[Steven D'Aprano]

On Sat, 23 Jul 2016 01:21 am, justin walters wrote:

> That should illustrate why. This is because simply typing '{}' could be
> interpreted as
> either a dict or a set. 

No. {} is always an empty dict. That is a language guarantee. Any
programming language where {} is not an empty disk is not valid Python.

> My interpreter defaults 'type({})' to 'dict', but it's best to not
> take the risk.

Are you concerned that type([]) might not be list? Or type("") might not be
str? Or that type(0) might not be int?

> You could also replace that line with:
> 
>     if stock is None or type(stock) != dict:

Generally speaking, the right way to test whether something is an instance
of a type is to use the isinstance() function:

if stock is None or not isinstance(stock, dict): ...


That will work correctly even if stock belongs to a subclass of dict.



-- 
Steven
“Cheer up,” they said, “things could be worse.” So I cheered up, and sure
enough, things got worse.