I feel stoopid ... this code is to verbose

[Gerson Kurz]

Correct me if I'm wrong, but all of the previous suggestions only seem
to insert dots, not dots and commas; i.e. you want the output like
this:

>>> 42.034.539.823,94

not

>>> 4.203.453.982.394

so here is my one liner:

strfmt = lambda x:"".join(map(lambda c,l,y=len(x):(l==3) and c+"," or
(not (l-3)%3 and c+"." or c),list(x),range(len(x),0,-1)))
    
print strfmt("4203453982394")

>>> 42.034.539.823,94

Of course, the statement in the above code should be written in one
line.