Does Ruby have any number formatting classes?

Try this:

1234567890.123.to_s.reverse.gsub(/(\d{3})(?=\d)/, '\\1,').reverse
=> "1,234,567,890.123"

Taken from a comment by @pguardiario in a similar thread

Ruby provides Kernel#format class method that looks more like the python 3.x method. Checkout Ruby's Docs for more details. This can be used to format both string and number.There are others like %e and %g for exponential and etc.

Below are some examples.

number use %f for float and %d for integer

format('%.2f', 2.0) #=> "2.00"

format('%.d', 2.0) #=> "2"

string use %s

format('%.4s', "hello") #=> "hell"

format('%6s', "hello") #=> " hello"

format('%-6s', "hello") #=> "hello "

You can use Kernel#sprintf (or Kernel#format) and do it that way. API Link.

Ruby has all the standard print formatters, available either via printf, sprintf or using 'formatstring' % [var1, ...].

>> '%.2f' % 3.14159 #=> "3.14"
>> '%4s %-4s' % ['foo', 'bar'] #=> " foo bar "