[Tutor] Why doesn't this work?
Jason Massey
jason.massey at gmail.com
Mon Jan 23 21:53:48 CET 2006
Christopher,
I copied and pasted your code and it worked only a few modifications. The
thing I had to change was the indention level of the:
def __and__(self, other): return self.intersect(other)
def __or__(self, other): return self.union(other)
def __repr__(self): return 'Set:' + list.__repr__(self)
statements. These statements need to be on the same indention level as your
__init__, intersection and union satements.
Here's what I got:
class Set(list):
def __init__(self, value=[]):
list.__init__([])
self.concat(value)
def intersect(self, other):
res = []
for x in self:
if x in other:
res.append(x)
return Set(res)
def union(self, other):
res = Set(self)
res.concat(other)
return res
def concat(self, value):
for x in value:
if not x in self:
self.append(x)
def __and__(self, other): return self.intersect(other)
def __or__(self, other): return self.union(other)
def __repr__(self): return 'Set:' + list.__repr__(self)
if __name__ == '__main__':
x = Set([1,3,5,7])
y = Set([2,1,4,5,6])
print x, y, len(x)
print x.intersect(y), y.union(x)
print x & y, x | y
x.reverse();
print x
On 1/23/06, Christopher Spears <cspears2002 at yahoo.com> wrote:
>
> I copied this code from Learning Python while learning
> about extending types by subclassing:
>
> class Set(list):
> def __init__(self, value=[]):
> list.__init__([])
> self.concat(value)
>
> def intersect(self, other):
> res = []
> for x in self:
> if x in other:
> res.append(x)
> return Set(res)
>
> def union(self, other):
> res = Set(self)
> res.concat(other)
> return res
>
> def concat(self, value):
> for x in value:
> if not x in self:
> self.append(x)
>
> def __and__(self, other): return self.intersect(other)
> def __or__(self, other): return self.union(other)
> def __repr__(self): return 'Set:' +
> list.__repr__(self)
>
> if __name__ == '__main__':
> x = Set([1,3,5,7])
> y = Set([2,1,4,5,6])
> print x, y, len(x)
> print x.intersect(y), y.union(x)
> print x & y, x | y
> x.reverse(); print x
>
> Here is the result:
>
> cspears at iaws09:/imports/home/cspears/Documents/Python/chap23>
> python setsubclass.py
> [1, 3, 5, 7] [2, 1, 4, 5, 6] 4
> [1, 5] [2, 1, 4, 5, 6, 3, 7]
> Traceback (most recent call last):
> File "setsubclass.py", line 32, in ?
> print x & y, x | y
> TypeError: unsupported operand type(s) for &: 'Set'
> and 'Set'
>
> According to the book, here is what I should get:
>
> Set:[1, 3, 5, 7] Set:[2, 1, 4, 5, 6] 4
> Set:[1, 5] Set:[2, 1, 4, 5, 6, 3, 7]
> Set:[1, 5] Set:[1, 3, 5, 7, 2, 4, 6]
> Set:[7, 5, 3, 1]
>
> Problem 1: Why isn't "Set:" being printed? I thought
>
>
> def __repr__(self): return 'Set:' +
> list.__repr__(self)
>
> would facilitate that.
>
> Problem 2: What is causing the TypeError?
>
> I'm pretty sure I copied this exactly from the book,
> so I'm not sure what is not working.
> _______________________________________________
> Tutor maillist - Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
>
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