Recursive Str?

[Chris S.]

Why do most, if not all, compound Python structures not convert their
elements to strings recursively?

class foo: .... def __init__(self, a):
.... self.a = a
.... def __str__(self):
.... return 'foo('+str(self.a)+')'
.... from sets import Set
a=Set([foo(1)])
print a Set([<__main__.foo instance at 0x01C01968>]) def SetStr(self): .... text = []
.... for n in self:
.... text.append(str(n))
.... return 'Set('+', '.join(text)+')'
.... Set.__str__ = SetStr
print a

Set(foo(1))

[Steven Bethard]

Chris S. <chrisks <at> NOSPAM.udel.edu> writes:

Why do most, if not all, compound Python structures not convert their
elements to strings recursively?

>>> class foo: ... def __init__(self, a):
... self.a = a
... def __str__(self):
... return 'foo('+str(self.a)+')'
... >>> from sets import Set
>>> a=Set([foo(1)])
>>> print a Set([<__main__.foo instance at 0x01C01968>])

Well, they call the __repr__ method, not the __str__ method:

class foo: .... def __init__(self, a):
.... self.a = a
.... def __str__(self):
.... return 'foo(%s)' % self.a
.... set([foo(1)]) set([<__main__.foo instance at 0x009D8030>]) class foo: .... def __init__(self, a):
.... self.a = a
.... def __repr__(self):
.... return 'foo(%s)' % self.a
.... set([foo(1)])

set([foo(1)])

Were you just looking for this behavior, or were you asking why it's __repr__
and not __str__?

Steve

[Chris S.]

Steven Bethard wrote:

Were you just looking for this behavior, or were you asking why it's __repr__
and not __str__?

Steve

Actually, it seems I'm confusing __str__ with __repr__. Now things make
sense. Thanks for the clarification.

[Steven Bethard]

Chris S. <chrisks <at> NOSPAM.udel.edu> writes:

Actually, it seems I'm confusing __str__ with __repr__. Now things make
sense. Thanks for the clarification.

You're welcome. Glad it was the easy question, not the hard one -- I never
did bother to look up the __repr__ vs. __str__ discussions on this topic. ;)

Steve