Classes, Instances and Attributes
Try it: Classes, Instances and Attributes
How a class creates instances with __init__ and self, why an attribute read checks the instance's __dict__ before the class, why assigning through an instance never changes the class, how a class-level list is shared by every instance, and why obj.method(x) is Class.method(obj, x).
How it works
- Dog(...) makes a new, empty instance and calls Dog.__init__(new_object, ...); self.name = ... stores into that object's __dict__.
- Reading obj.attr looks in obj.__dict__ first, then in the class.
- Assigning obj.attr = value always writes obj.__dict__, so it shadows a class attribute for that one object only.
- Mutating a class-level list (self.tricks.append) changes the one list every instance shares.
- obj.method is found on the class and bound to obj, so obj.method(x) runs Class.method(obj, x).
Default run (30 steps): Ready: class Dog and the statements you picked. Watch where each attribute is found and where each assignment writes. … Finished. Printed: ['sit'] / Wolf / Canis familiaris / Fido is 5.
Simplified: The lab's own small Python interpreter runs a fixed, hand-written script (you choose the variant and the values, never the code); nothing is executed as real Python. Every script was run in CPython 3.12 with the same inputs and the lab reproduces its output and error messages. Object numbers are illustrative, not real id() values.
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