Differences between the following python and ruby code

Question

I was trying to solve the following problem: https://www.codeeval.com/open_challenges/23/

This was my solution in Python, which didn't pass:

for x in range(1,13):
    string = ''
    for y in range(1,13):
        string += ' '*(4-len(str(x*y))) + str(x*y)
    print string.strip()

This was my friend's solution in Ruby, which did pass:

for i in 1..12
  line = ""
  for j in 1..12
    line += " " * (4 - (j * i).to_s.length) + "#{j * i}"
  end
  puts line.strip
end

To me, the two snippets look like they do the same thing and they output the same thing based on my testing. Do you think there is a reason my solution isn't being accepted other than issues with the evaluation system?

don't call a string string and use string formatting to align stuff — Fredrik Pihl
– Fredrik Pihl, Commented Feb 24, 2014 at 16:52
I don't know Ruby, but may be because better way of writing code in Python is something like that @Martijn's answered — Grijesh Chauhan
– Grijesh Chauhan, Commented Feb 24, 2014 at 16:57
for i in 1..12 is almost always better written as 12.times do |i| or (1..12).each do |i| as it's extremely unusual to see for used in Ruby code. — tadman
– tadman, Commented Feb 24, 2014 at 16:57

Martijn Pieters · Accepted Answer · 2014-02-24 16:57:56Z

2

I'd use:

for x in range(1, 13):
    print ''.join([format(x * y, '2d' if y == 1 else '4d') 
                   for y in range(1, 13)])

This formats the left-most column to hold at most 2 characters (1 through to 12), 4 characters otherwise, right-aligned.

Your version removes too much whitespace from the start of the lines; the last 3 lines need space for 2 digits in the left-most column.

edited Feb 24, 2014 at 16:57

answered Feb 24, 2014 at 16:51

Martijn Pieters

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4 Comments

wim Over a year ago

But so does the ruby version, which was apparently accepted.

Martijn Pieters Over a year ago

@wim: I don't know enough Ruby to judge that, but it could be that there is a bug in the challenge checker for Ruby.

Martijn Pieters Over a year ago

@wim: another option is that the friend is pulling OPs leg and hasn't yet passed the challenge.

Zack Gao Over a year ago

No I tried to submit the Ruby solution and it did pass. Thank you for the suggested approach though. It worked.

tadman · Accepted Answer · 2014-02-24 17:03:21Z

1

Answer in Ruby for comparison:

(1..12).each do |i|
  puts((1..12).collect do |j|
    '%4d' % (i * j)
  end.join(' '))
end

The '%4d' makes use of sprintf-style formatting to properly pad without needing to test lengths.

answered Feb 24, 2014 at 17:03

tadman

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