bool and int

[avi.e.gross at gmail.com]

Python yet again is being asked why something is the way it is and not as
someone insists it should be. It is a tool to be used the way it SAYS it
works so the bug is perhaps in the user and their expectations.

It is what it is and would break lots of things if changed without much
thought. Every other language I know has similar detractors asking why it is
the way it is.

A useful example where the use of Booleans as 0/1 is commonly used is to
find how many of something satisfy some criteria, such as how many items in
a list are numbers greater than 65 representing test scores that "passed".
It could also be a numpy type of array or a column of a data.frame and so
on. The common method is to create a Boolean data structure (often
implicitly) that is then viewed as a bunch of 0's and 1's and you can count
them to see how many are True (meaning they qualify) or calculate a
percentage simply by taking a mean of the 0/1 values.

There are other ways, but some also use sums of Booleans to calculate things
like any() or all() and I am sure many other things. Yes, all these can be
done another way if Booleans were not allowed to be viewed as very small
integers.

So only use a Boolean in relatively pure situations where arithmetic as a
zero or one is meaningful. In other places, maybe don't. The reality though
is that if you have 10 apples and you get another one if you flip a coin and
it lands on heads. Then 10 + Boolean would indeed be 11. If you have five
losing flips (or tickets or whatever) then 5 * Boolean indeed is a zero. 

Python has a different philosophy than some other languages with strong
typing. In some of those, you would not be allowed to add or multiply at
random but would need to convert parts of your calculation to all be the
same, such as a 32-bit integer. You could still do things like I mention
above but only after consciously mapping your Boolean to an actual zero or
one of the kind wanted. 

I worry a tad more about the other direction where something like an integer
containing a number like 12 is used in a context where it gets downgraded to
a True/False and later may inadvertently be used as a "1" as the conversion
is not anticipated. There is data loss there more than in the case of a
Boolean becoming a 1.

-----Original Message-----
From: Python-list <python-list-bounces+avi.e.gross=gmail.com at python.org> On
Behalf Of 2QdxY4RzWzUUiLuE at potatochowder.com
Sent: Tuesday, January 24, 2023 6:31 PM
To: python-list at python.org
Subject: Re: bool and int

On 2023-01-25 at 08:58:06 +1100,
Chris Angelico <rosuav at gmail.com> wrote:

> On Wed, 25 Jan 2023 at 08:22, MRAB <python at mrabarnett.plus.com> wrote:
> > For backwards compatibility, bool was made a subclass of int.
> 
> Plus, it's really REALLY handy in quite a lot of situations.
> 
> > > C# is pickier, which I guess is a good thing.
> >
> 
> Nope, not a good thing. Actually a highly frustrating thing on those 
> occasions when I have to write C# code.

The usual complaint is that some people write FORTRAN no matter what
language they're actually using.  Are you writing Python in C#?  ;-)

There's a sweet spot somewhere that includes dynamic typing, high powered
global type inference and optimization systems, a thriving community, and a
metric [boatload] of rock solid libraries.

And an alomost fanatical devotion to the Pope.  :-/
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