"Peter Hansen" <[EMAIL PROTECTED]> wrote:

> Jp Calderone wrote:
> > On Sat, 16 Jul 2005 19:01:50 -0400, Peter Hansen <[EMAIL PROTECTED]> wrote:
> >> George Sakkis wrote:
> >>>>>> identity = string.maketrans('','')
> >>
> >> Wow!  That's handy, not to mention undocumented.  (At least in the
> >> string module docs.)  Where did you learn that, George?
> >>
> > http://python.org/doc/lib/node109.html
> Perhaps I was unclear.  I thought it would be obvious that I knew where
> to find the docs for maketrans(), but that the particular behaviour
> shown (i.e. arguments of '' having that effect) was undocumented in that
> page.
> -Peter

Actually I first read about this in the Cookbook; there are two or three 
recipes related to
string.translate. As for string.maketrans, it doesn't do anything special for 
empty string

      maketrans( from, to)

Return a translation table suitable for passing to translate() or 
regex.compile(), that will map
each character in from into the character at the same position in to; from and 
to must have the same

So if from and to are empty, maketrans will map zero characters, hence the 
identity. It's not the
only way to get the identity translation table by the way:
>>> string.maketrans('', '') == string.maketrans('a', 'a') == 
>>> string.maketrans('hello', 'hello')



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