How to format a number 1000 as “1 000”

Question

I need a way to format numbers. I stored some numbers in my DB table, e.g. 12500, and would like to print them in this format 12 500 (so there is a

Answer 1

The official document suggests three different ways:

1) Using lookbehind and lookahead (Requires oniguruma)

12500.to_s.gsub(/(?<=\d)(?=(?:\d{3})+\z)/, ' ')
# => "12 500"

2) Using only lookahead. Identical to steenslag's answer.

3) Using neither lookahead nor lookbehind

s = 12500.to_s
nil while s.sub!(/(.*\d)(\d{3})/, '\1 \2')
s # => "12 500"