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

[C W]

Thanks so much everyone, I appreciate it!

Ming, your solution is awesome. More importantly, very clear explanations
on how and why. So, I appreciate that.

Thanks again, cheers!

Mike

On Sun, Feb 21, 2021 at 12:08 AM <2QdxY4RzWzUUiLuE at potatochowder.com> wrote:

> 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."
> --
> https://mail.python.org/mailman/listinfo/python-list
>