possible to round number and convert to string?

[superpollo]

Dr. Phillip M. Feldman wrote:
> I'd like to be able to convert a float to a string representation in which
> the number is rounded to a specified number of digits.  If num2str is a
> hypothetical function that does this, then num2str(pi,3) would be '3.142'
> (not '3.141').  I've been told that there is no such function in Python.  I
> tried to write this myself, but wasn't successful.  Any suggestions will be
> appreciated.

 >>> import math
 >>> s = str(round(math.pi, 3))
 >>> s
'3.142'
 >>>