F commatize(s, period = 3, sep = ‘,’)
   V m = re:‘(\.[0-9]+|[1-9]([0-9]+)?(\.[0-9]+)?)’.search(s)
   I !m
      R s

   V match = m.group()
   V splits = match.split(‘.’)

   V ip = splits[0]
   I ip.len > period
      V inserted = 0
      L(i) ((ip.len - 1) % period + 1 .< ip.len).step(period)
         ip = ip[0 .< i + inserted]‘’sep‘’ip[i + inserted ..]
         inserted += sep.len

   I splits.len > 1
      V dp = splits[1]
      I dp.len > period
         L(i) ((dp.len - 1) I/ period * period .< period - 1).step(-period)
            dp = dp[0 .< i]‘’sep‘’dp[i..]
      ip ‘’= ‘.’dp

   R s[0 .< m.start()]‘’ip‘’s[m.end()..]

V tests = [‘123456789.123456789’,
           ‘.123456789’,
           ‘57256.1D-4’,
           ‘pi=3.14159265358979323846264338327950288419716939937510582097494459231’,
           ‘The author has two Z$100000000000000 Zimbabwe notes (100 trillion).’,
           ‘-in Aus$+1411.8millions’,
           ‘===US$0017440 millions=== (in 2000 dollars)’,
           ‘123.e8000 is pretty big.’,
           ‘The land area of the earth is 57268900(29% of the surface) square miles.’,
           ‘Ain't no numbers in this here words, nohow, no way, Jose.’,
           ‘James was never known as 0000000007’,
           ‘Arthur Eddington wrote: I believe there are ’""
             ‘15747724136275002577605653961181555468044717914527116709366231425076185631031296’""
             ‘ protons in the universe.’,
           ‘   $-140000±100 millions.’,
           ‘6/9/1946 was a good year for some.’]

print(commatize(tests[0], period' 2, sep' ‘*’))
print(commatize(tests[1], period' 3, sep' ‘-’))
print(commatize(tests[2], period' 4, sep' ‘__’))
print(commatize(tests[3], period' 5, sep' ‘ ’))
print(commatize(tests[4], sep' ‘.’))

L(test) tests[5..]
   print(commatize(test))