In article <[EMAIL PROTECTED]>, George Trojan <[EMAIL PROTECTED]> wrote:
> A while ago I found somewhere the following implementation of frange(): > > def frange(limit1, limit2 = None, increment = 1.): > """ > Range function that accepts floats (and integers). > Usage: > frange(-2, 2, 0.1) > frange(10) > frange(10, increment = 0.5) > The returned value is an iterator. Use list(frange) for a list. > """ > if limit2 is None: > limit2, limit1 = limit1, 0. > else: > limit1 = float(limit1) > count = int(math.ceil(limit2 - limit1)/increment) > return (limit1 + n*increment for n in range(count)) > > I am puzzled by the parentheses in the last line. Somehow they make > frange to be a generator: > >> print type(frange(1.0, increment=0.5)) > <type 'generator'> > But I always thought that generators need a keyword "yield". What is > going on here? Hi, George, The expression returned is a "generator expression", return (limit1 + n*increment for n in range(count)) Thus, although frange itself is not written as a generator, it does return a generator as its result. The syntax is like that of list comprehensions; see: <http://docs.python.org/ref/genexpr.html> Cheers, -M -- Michael J. Fromberger | Lecturer, Dept. of Computer Science http://www.dartmouth.edu/~sting/ | Dartmouth College, Hanover, NH, USA -- http://mail.python.org/mailman/listinfo/python-list
