learnpython.org - an online interactive Python tutorial

harrismh777 harrismh777 at charter.net
Thu Apr 21 09:29:00 CEST 2011


Algis Kabaila wrote:
> [quote]
> Python is completely object oriented, and not "strongly typed"
> [/quote]
>
> False: Python IS strongly typed, without doubt (though the
> variables are not explicitly declared.)
>


Playing the advocate for a moment here, this is something that I was 
confused about early on also... and frankly, you are both correct, but 
from different vantage points.

Python IS strongly typed in that operations may only be applied to 
objects that support 'that' operation... numbers support (+) and also 
strings support (+) ,  although, the (+) does 'different' things 
depending on the object type. You might look at this as STRONGLY typed 
and you would be correct...  however, you might look on this as weakly 
typed and you would still be correct... because why?

Because, the programmer doesn't have to worry about the 'types' she is 
using ... the object based nature of the language and polymorphism come 
together so that the 'right thing' happens with (+) regardless of 
type...   see?  weakly typed...

In C the programmer is always considering what 'type' is this thing... 
even testing for it... and C is considered by those programmers (yes, me 
) as STRONGLY typed. The types must be declared ahead of time for sure, 
but that's not the point...  the point is that the 'type' matters and 
must always be on the front lobes in thinking about logic.

In Python much of the thinking about types is not even necessary.. for 
the most part... and by design. In this way of thinking the language is 
weakly typed...  on the other hand, because the objects may be only 
manipulated by operations they support, this makes Python STRONGLY 
typed.   Confused yet???

How one thinks about this depends on programming background, what is 
meant by 'type' and how the programmer differentiates thinking about 
types as variables versus objects.

Having said all of that, I agree that Python should be classified as 
STRONGLY typed... and this classification should always come with an 
explanation ... especially to new advocates writing tutorials...

kind regards,
m harris



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