Is there a way to subtract 3 from every digit of a number?

[2QdxY4RzWzUUiLuE at potatochowder.com]

On 2021-02-20 at 20:49:15 -0800,
Dan Stromberg <drsalists at gmail.com> wrote:

> On Sat, Feb 20, 2021 at 7:13 PM Ming <ming at pgp.cool> wrote:
> 
> > I just wrote a very short code can fulfill your needs:
> >
> > a = 2342
> > b = int("".join(map(lambda x: str((int(x)-3)%10) ,list(str(a)))))
> >
> I tend to favor plenty of temporary variables with descriptive names, but
> this is indeed short.
> 
> Apart from that, you may find that using a generator expression is shorter
> and clearer than map+lambda.  It should allow to additionally eliminate the
> list conversion.
> 
> So in the terse form you've got there, it'd be more like:
> b =  int(''.join(str((int(x) - 3) % 10) for x in str(a))
> 
> But in real life, I'd try to use descriptive variable names for some of the
> subexpressions in that.  This makes reading and debugging simpler, which is
> important because the maintenance phase of software is almost always much
> longer and costly than the development phase.  And although you could do a
> generator expression for each of the different parts of (int(x) - 3) % 10,
> I kinda like having a named function for just that piece.
> 
> So maybe:
>   def rot_3(character):
>       """Convert to int, subtract 3 and mod 10."""
>       digit = int(character)
>       assert 0 <= digit <= 9
>       return (digit - 3) % 10
> 
> 
>   def descriptive_minus_three_caesar(input_number):
>       """Convert to a -3 caesar cypher on an integer."""
>       string_number = str(input_number)
>       rotated_digits = (rot_3(character) for character in string_number)
>       output_string = ''.join(str(digit) for digit in rotated_digits)
>       output_number = int(output_string)
>       return output_number

>>> descriptive_minus_three_caesar('38')
5

The problem is underspecified, and the examples are lacking, but based
on the phrase "each digit" and the examples that contain a 3, I'd prefer
to see "38" become "05."