diff -r ffa851df0825 -r 2fb8b9db1c86 symbian-qemu-0.9.1-12/python-2.6.1/Demo/classes/Range.py --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/symbian-qemu-0.9.1-12/python-2.6.1/Demo/classes/Range.py Fri Jul 31 15:01:17 2009 +0100 @@ -0,0 +1,93 @@ +"""Example of a generator: re-implement the built-in range function +without actually constructing the list of values. + +OldStyleRange is coded in the way required to work in a 'for' loop before +iterators were introduced into the language; using __getitem__ and __len__ . + +""" +def handleargs(arglist): + """Take list of arguments and extract/create proper start, stop, and step + values and return in a tuple""" + try: + if len(arglist) == 1: + return 0, int(arglist[0]), 1 + elif len(arglist) == 2: + return int(arglist[0]), int(arglist[1]), 1 + elif len(arglist) == 3: + if arglist[2] == 0: + raise ValueError("step argument must not be zero") + return tuple(int(x) for x in arglist) + else: + raise TypeError("range() accepts 1-3 arguments, given", len(arglist)) + except TypeError: + raise TypeError("range() arguments must be numbers or strings " + "representing numbers") + +def genrange(*a): + """Function to implement 'range' as a generator""" + start, stop, step = handleargs(a) + value = start + while value < stop: + yield value + value += step + +class oldrange: + """Class implementing a range object. + To the user the instances feel like immutable sequences + (and you can't concatenate or slice them) + + Done using the old way (pre-iterators; __len__ and __getitem__) to have an + object be used by a 'for' loop. + + """ + + def __init__(self, *a): + """ Initialize start, stop, and step values along with calculating the + nubmer of values (what __len__ will return) in the range""" + self.start, self.stop, self.step = handleargs(a) + self.len = max(0, (self.stop - self.start) // self.step) + + def __repr__(self): + """implement repr(x) which is also used by print""" + return 'range(%r, %r, %r)' % (self.start, self.stop, self.step) + + def __len__(self): + """implement len(x)""" + return self.len + + def __getitem__(self, i): + """implement x[i]""" + if 0 <= i <= self.len: + return self.start + self.step * i + else: + raise IndexError, 'range[i] index out of range' + + +def test(): + import time, __builtin__ + #Just a quick sanity check + correct_result = __builtin__.range(5, 100, 3) + oldrange_result = list(oldrange(5, 100, 3)) + genrange_result = list(genrange(5, 100, 3)) + if genrange_result != correct_result or oldrange_result != correct_result: + raise Exception("error in implementation:\ncorrect = %s" + "\nold-style = %s\ngenerator = %s" % + (correct_result, oldrange_result, genrange_result)) + print "Timings for range(1000):" + t1 = time.time() + for i in oldrange(1000): + pass + t2 = time.time() + for i in genrange(1000): + pass + t3 = time.time() + for i in __builtin__.range(1000): + pass + t4 = time.time() + print t2-t1, 'sec (old-style class)' + print t3-t2, 'sec (generator)' + print t4-t3, 'sec (built-in)' + + +if __name__ == '__main__': + test()