What's the best way to minimize the need of run time checks?

[MRAB]

On 2016-08-09 19:57, Chris Angelico wrote:
> On Wed, Aug 10, 2016 at 4:51 AM, Michael Selik <michael.selik at gmail.com> wrote:
>> "File-like" is a good example. Rather than go through the frustration of a
>> formal definition for what is file-like, stay productive and flexible with
>> duck typing. Objects that don't have the appropriate methods or attributes
>> will cause a TypeError or AttributeError. If you're passing in the wrong
>> kind of object, you'll find out almost as soon as you write the code
>> (because you test early and often), just as you would with a statically
>> analyzed type system.
>
> It's slightly delayed; with Python, you have to actually execute the
> code path in question, whereas a static type system would detect it at
> the compilation stage. So it may depend on the quality of your
> testing. MyPy may be able to help there.
>
Static checking won't tell you if, say, you're adding when you should be 
subtracting, so you'd need to execute the code path in question anyway 
during testing!