Questions about subclassing an int

Steven W. Orr steveo at
Fri Jan 4 23:55:33 CET 2008

class S(int):
     def __init__(self, value):
 	self.value = value
     def addStr(self, str):
 	self.doc = str

s = S(44)

print 's = ', s
print 's.doc = ', s.doc

class T(int):
     def __init__(self, value, str):
 	self.value = value
 	self.doc = str

t = T(44, 'Goodbye')

print 't = ', t
print 't.doc = ', t.doc

It works ok with S but it fails when I try to instantiate T with a syntax 
error. Why?

Also, I don't understand why S works. If I change the name of value and 
use something else, the print of s still works by printing the integer 
value out. How does it know what value to use? Also, in S.__init__, should 
I be calling super(S, self).__init__(value) or is there a difference?

And just for fun:

class R(int):
     def __init__(self, value, doc):
         super(R, self).__init__(value)
         self.doc = doc

r = R(66,'GGG')
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
TypeError: an integer is required

Now it's no longer a syntax error but I don't see why it's different?

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steveo at

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