Generate a random number with 7 digits

Question

How can I produce a random number in a range from 1 million to 10 million?

rand(10) works, I tried rand(1..10) and that didn't work.

score 13 · Accepted Answer · answered Apr 19 '11 at 21:35

13

Take your base number, 1,000,000 and add a random number from 0 up to your max - starting number:

 1_000_000 + Random.rand(10_000_000 - 1_000_000) #=> 3084592

answered Apr 19 '11 at 21:35

the Tin Man

I'm using ruby 1.8.7, Random doesnt' seem to exist. is it a gem? – Blankman Apr 19 '11 at 22:26
@Blankman: Did you try `require 'random'`, and also checking if it's 1.9.2 only? – Andrew Grimm Apr 19 '11 at 22:41
1.8.7 doesn't have Random. It's in 1.9.2+. Install the backports gem and you'll inherit it in 1.8.7, along with lots of other juicy goodness. – the Tin Man Apr 19 '11 at 23:41
what are the ramifications of installing backport? (if any) – Blankman Apr 20 '11 at 01:15
4

Just use `rand`, not `Random.rand`. It works all the way back as far as 1.6.0 – Joshua Cheek Apr 20 '11 at 13:10

steenslag · Answer 2 · 2011-04-19T21:53:24.427

6

It's an instance method:

puts Random.new.rand(1_000_000..10_000_000-1)

edited Apr 19 '11 at 21:53

answered Apr 19 '11 at 21:46

steenslag

score 3 · Answer 3 · answered Mar 17 '17 at 13:41

3

I find this more readable:

7.times.map { rand(1..9) }.join.to_i

answered Mar 17 '17 at 13:41

Arturo Herrero

Sebastian · Answer 4 · 2013-06-11T20:40:35.143

1

Or, in case performance is not an issue and you don't want to count zeros:

(0...7).map { |i| rand((i == 0 ? 1 : 0)..9) }.join.to_i

edited Jun 11 '13 at 20:40

answered Jun 09 '13 at 21:16

Sebastian

score 1 · Answer 5 · answered Apr 19 '11 at 23:49

1

This will generate a random number between 1,000,000 and 9,999,999.

rand(10_000_000-1_000_000)+1_000_000

This works in 1.8.7 without any gems(backports, etc).

answered Apr 19 '11 at 23:49

Mike Lewis

score 0 · Answer 6 · answered Jan 24 '13 at 12:20

0

Another option with ruby 1.8.7 compatibility:

rand(9999999999).to_s.center(10, rand(9).to_s).to_i

answered Jan 24 '13 at 12:20

Paulo Fidalgo

6 Answers6