Bools and explicitness [was Re: PyWart: The problem with "print"]

[Chris Angelico]

On Thu, Jun 6, 2013 at 11:56 AM, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> On Wed, 05 Jun 2013 14:59:31 -0700, Russ P. wrote:
>> As for Python, my experience with it is that, as
>> your application grows, you start getting confused about what the
>> argument types are or are supposed to be.
>
> Whereas people never get confused about the arguments in static typed
> languages?
>
> The only difference is whether the compiler tells you that you've passed
> the wrong type, or your unit test tells you that you've passed the wrong
> type. What, you don't have unit tests? Then how do you know that the code
> does the right thing when passed data of the right type? Adding an extra
> couple of unit tests is not that big a burden.

The valid type(s) for an argument can be divided into two categories:
Those the compiler can check for, and those the compiler can't check
for. Some languages have more in the first category than others, but
what compiler can prove that a string is an
HTML-special-characters-escaped string? In a very few languages, the
compiler can insist that an integer be between 7 and 30, but there'll
always be some things you can't demonstrate with a function signature.

That said, though, I do like being able to make at least *some*
declaration there. It helps catch certain types of error.

ChrisA