Base conversion in python

Question

I need help to understand this question. Please don't post the answer, only the ways to solve it.

Assign 10 to the variable base. Assign the set {0,1,2,3,4,5,6,7,8,9} to the variable digits. Now write an expression using a comprehension and base and digits whose value is the set of all at-most- three-digit numbers. Your expression should work for any base. For example, if you instead assign 2 to base and assign {0,1} to digits, the value of your expression should be {0,1,2,3,4,5,6,7} because this is the set of numbers that, base two, have at most three digits.

I try this expression but I could not solve the base 2 question.

base = 10
digits = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
{(x*(base**2))+(y*(base**1))+(z*(base**0)) for x in digits for y in digits for z in digits if (x*(base**2))+(y*(base**1))+(z*(base**0))>((y*(base**1))+(z*(base**0)))}

I would recomend finding the largest value in the set of digits. I would then just do range(int('%s%s%s'%(max_digit,max_digit_max_digit),base)+1) but that probably isnt what your teacher wants — Joran Beasley
– Joran Beasley, Commented Jul 8, 2013 at 20:13
I need to come up with a comprehension that return a {100-999} set for decimals and the same expression should work with any base ex: 2,8 16... — Rodrigo Camargos
– Rodrigo Camargos, Commented Jul 8, 2013 at 20:20
I recognise this question as being from the Coursera matrix/linear algebra course. You should really look on the course discussion board there, rather than asking for help here. — Daniel Roseman
– Daniel Roseman, Commented Jul 8, 2013 at 20:27
your code seems to work fine ... "At most 3 characters" not "exactly 3 characters" ... just get rid of the if in the comprehension — Joran Beasley
– Joran Beasley, Commented Jul 8, 2013 at 20:27
Actually you need to come up with a generator that will give you all the three digit numbers in the range 001 to MMM where M is max digit this will automatically include the one and two digit numbers by allowing leading 0s. The other hints look at the output of python -c "print help(int)"... — Steve Barnes
– Steve Barnes, Commented Jul 8, 2013 at 20:29

Bill the Lizard · Accepted Answer · 2013-07-08 20:26:48Z

2

...whose value is the set of all at-most- three-digit numbers.

Emphasis added. You need to include the values 000 - 099 (for base = 10).

It looks like you've almost got it. You don't need a filter in your comprehension. Think about how many results you'll get from for x in digits for y in digits for z in digits for different values in digits. It should be exactly the right number of values.

answered Jul 8, 2013 at 20:26

Bill the Lizard

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dkar · Accepted Answer · 2013-07-15 19:03:03Z

1

You already had the answer, simply remove the if statement. Try this:

{x*base**2+y*base**1+z*base**0 for x in digits for y in digits for z in digits}

If you use base 10 and digits (0,1,2,3,4,5,6,7,8,9) you should get a list from from 0 to 999. And if you use base 2 and digits (0,1) you should get a list from 0 to 7.

edited Jul 15, 2013 at 19:03

dkar

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answered Jul 15, 2013 at 18:42

Moisés Pacheco Gendrop

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Bacon · Accepted Answer · 2015-05-12 07:06:38Z

1

As I guess your homework is done, almost two years later:

The number of 3 digits number within your base is a sequence of the form

base^digits

For example, to have the number of 3-digits numbers in base ten, one would type in python:

10**3

You then can use the range function to have them all:

{x for x in range(10**3)}

This works with any base.

answered May 12, 2015 at 7:06

Bacon

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