[roger64]

@DiapDealer

Crossing the fingers, here is pingouin2 which takes into account your previous remark.

#!/usr/bin/python

import sys, re

conv=2.37106301584
unit=re.compile('(:\s*)(-?[\d.]+)(cm)?(;|})')
with open(sys.argv[1],'r') as f, open(sys.argv[2],'w') as g :

   fic=f.read()

   while True :
      k=unit.search(fic)
      if(k) :
         g.write(fic[:k.start(1)])
         g.write(k.group(1))
         val=k.group(2)
         unite=k.group(3)
         if unite=='cm' :
            val="%.2f"%(conv*float(k.group(2)))
            unite='em'
         else : unite=''
         g.write(val+unite)
         g.write(k.group(4))
         fic=fic[k.end(4):]
      else :
         g.write(fic)
         break

With the new release, I will make another round of testing involving some other people. I suppose this release will also be working for both Python 2.x and 3.x. If you take Kovid Goyal's advice, please provide some comments as this is way above my head.