netimen a écrit :
I couldn't substitute __str__ method of an instance. Though I managed
to substitute ordinary method of an instance:
from types import MethodType
class Foo(object):
pass
class Printer(object):
def __call__(self, obj_self):
return 'printed'
f = Foo()
f.printer = MethodType(Printer(), f, Foo)
print f.printer() # works fine - I get: 'printed'
print f # get: <__main__.Foo object at 0x00D69C10>
f.__str__ = MethodType(Printer(), f, Foo)
print f # still get: <__main__.Foo object at 0x00D69C10>. Why?
Foo.__str__ = MethodType(Printer(), None, Foo)
print f # works fine - I get: 'printed'
How can I substitute __str__ method of an instance?
Now that others told you you couldn't do so, there's eventually a
workaround - that is, if you have the hand on class Foo:
class Foo(object):
def __str__(self):
printer = getattr(self, 'printer', super(Foo, self).__str__)
return printer()
HTH
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