Thoughts on PEP284

Sean Ross sross at connectmail.carleton.ca
Tue Sep 23 16:40:30 CEST 2003


Here's a quick hack of an int class that supports iteration using the slice
notation, plus simple iteration on the class itself (for i in int: ...).
This can certainly be improved, and other issues need to be addressed, but I
just wanted to see what Stephen's idea would look like in practice. (Not
bad. Actually, pretty good.)

# using python 2.2.2
from __future__ import generators

class xint(int):
    class __metaclass__(type):
        def __iter__(cls):
            return cls.__getitem__()
        def __getitem__(cls, index=None):
            if hasattr(index, "start"):
                for i in range(index.start, index.stop, index.step):
                    yield i
            elif isinstance(index, int):
                yield index
            elif index is None:
                i = 0
                while True:
                    yield i
                    i += 1
            else:
                raise Exception
        __getitem__ = classmethod(__getitem__)

print "iteration on int"
for i in xint:
    if i >= 10:
        break
    print i

print "\niteration on int slice"
for i in xint[0:22:2]:
    print i



#
# OUTPUT
#
iteration on int
0
1
2
3
4
5
6
7
8
9

iteration on int slice
0
2
4
6
8
10
12
14
16
18
20







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