Salvatore a écrit : > Thank's everybody :-) > > > Here is a type définition I've found on the net which I agree with : > > Attribute of a variable which determines the set of the values this > variabe can take and the > operations we can apply on it.
Then - as already pointed by Alex - there is no type in Python, since there is no variable (even if this term is often improperly used for bindings) !-) Ok, let's s/variable/object/g and define some objects and operations: def myop(obj): return obj.foo * 2 class Bar(object): pass b = Bar() Can we apply the myop() operation on the object name 'b' is bound to ? myop(b) Traceback (most recent call last): File "<stdin>", line 1, in ? File "<stdin>", line 1, in myop AttributeError: 'Bar' object has no attribute 'foo' Well... but wait a minute: b.foo = [] myop(b) -> [] Err... Wait another minute: b2 = Bar() type(b) is type(b2) -> True myop(b2) Traceback (most recent call last): File "<stdin>", line 1, in ? File "<stdin>", line 1, in myop AttributeError: 'Bar' object has no attribute 'foo' Ok, so even if Python itself declares b and b2 (read: objects that names b and b2 are bound to) to be of the same type, you cannot apply the myop() operation on b2... Also: del b.foo myop(b) Traceback (most recent call last): File "<stdin>", line 1, in ? File "<stdin>", line 1, in myop AttributeError: 'Bar' object has no attribute 'foo' So *sometimes* you can apply myop() to b, and sometimes you can't. Now if we come back to your original post: """ All objects seem to have a perfectly defined type """ "Perfectly defined" ? Really ? Not for your current definition of 'type' at least !-) I still mostly agree with the given definition of type. But the fact is that in Python, the type*s* of an object are not so perfectly defined - they're mostly implicits, and can vary during the object's lifetime. Note that it does'nt make Python weakly typed - you cannot perform any arbitrary operation on a given object, only the operations this object can support at a given moment. FWIW, if you want a weakly typed language, take a look at C. -- http://mail.python.org/mailman/listinfo/python-list
