Dear Group:
I am a little perplexed by a basic example from the O'Reilly book, 2nd ed.,
which demonstrates overloading some builtin list operators by embedding
lists in a wrapper class.
Below is a snippet which shows the wrapper class and the overloaded
operator definition within (in this case, '__or__')
## BEGIN SNIPPET (from setwrapper.py)
class Set:
def __init__(self, value = []):
self.data = []
self.concat(value)
def union(self, other):
res = self.data[:]
for x in other:
if not x in res:
res.append(x)
print 'using Set.__or__' #for debugging
return Set(res)
def __repr__(self):
return 'Set: ' + `self.data` #for debugging
def __or__(self, other):
return self.union(other)
## END SNIPPET
The problem is that I can't seem to get my wrapped lists to use the
overloaded versions of the operators without calling the customize
instance method directly, as shown below:
>>> import setwrapper; from setwrapper import *
>>> S1 = Set(['s','p','a','m'])
>>> S2 = Set(['s','c','a','t'])
>>> print S1 or S2
Set: ['s', 'p', 'a', 'm'] # custom __repr__ used but still default
# __or__ behavior, returns first true operand
>>> print S1.__or__(S2)
using Set.__or__
Set: ['s', 'p', 'a', 'm', 'c', 't'] # now all the custom behaviors
This happens regardless of whether the module is imported into IDLE, or run
standalone. Obviously I'm missing something very basic namespace issue, and
I don't want to gloss over any bumps in my learning curve.
Many thanks.
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