What is considered an "advanced" topic in Python?

[Rustom Mody]

On Monday, June 1, 2015 at 1:28:53 PM UTC+5:30, Laura Creighton wrote:
> If you are giving a talk about Decimal -- and trying to stamp out the
> inappropriate use of floats you have to first inform people that
> what they learned as 'decimals' as children was not floating point,
> despite the fact that we write them the same way.
> 
> If I ever get the time machine, I am going back in time and demand that
> floating point numbers be expressed as 12345:678 instead of 12345.678
> because it would save so much trouble.  Never has the adage 'It's not
> what you don't know, that bites you.  It's what you know that ain't so.'
> been more apt.
> 
> I have done much better in speaking about this topic to a bunch of
> incredulous people if you next explain that scientists really don't
> care about accuracy in their calculations.  (This will surprise them).
> Most scentific calculations have some real world measurement in them,
> and for most real world measurements, if you are getting even 5 digits
> of precision, you are doing really, really, well.  This means that
> scientists are going to be throwing away all the extra digits they get
> out a a floating point representation, so they don't have to care how
> accurate they are.  As long as their results are good in the first 5,
> it won't matter.  (Depending on time constraints, a review of
> significant figures -- what they are and what they mean is good here.)
> 
> It is really hard to get the concept of Decimal across to people who
> already have that concept in their mind, but think it is called Float.
> You have to first teach them that they don't know anything about Float
> and get them to reboot their brains before you can install this new
> knowledge.  Otherwise their brains will just overwrite your new knowledge
> with 'ah, just use a Float' as soon as you stop speaking.  Same day,
> even.
> 
> Laura

I'd say on the whole this *intention* is rightly directed.
Whether it would work in practice I am not sure.
You may like to look at haskell's defaulting mechanism which is about as
sophisticated as I have seen
https://www.haskell.org/tutorial/numbers.html [sect 10.4]
Basically: (the ':t' says give me the type of...)

Prelude> :t 4
4 :: Num a => a
Prelude> :t 1.0
1.0 :: Fractional a => a

What this says is that 4 is not an integer but any type that is in the Num class
Likewise 1.0 is not float but any of a family of 'Fractional' types.

Your ':' suggestion would work if Decimal and machine floats covered all needs.
Do you think that is possible/likely?
If not we would have to fall back to some 'defaulting' mechanism anyway.
[In all fairness while Haskell's default looks neat on paper it turns out to
be quite a nuisance in practice]