Python · The Data Model: Identity & Mutability

Every non-speed: a colleague checks if x is 1000: and it returns False even though x == 1000. What's the rule that explains both this and why x is 256 sometimes 'works'?

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More in The Data Model: Identity & Mutability

Predict the output: ``` v1 = [1, 2, 3] v2 = v1 v3 = [1, 2, 3] print(v1 == v3, v1 is v3) print(v1 == v2, v1 is v2) ```

Does assignment b = a copy the object that a refers to?

Predict the output: ``` a = "water " b = a a += "bottle" print(a) print(b) ```

Predict the output: ``` a = [1, 2] b = a a += [3, 4] print(a) print(b) ```

Why does the SAME += line leave an aliased str untouched but mutate an aliased list?

Classify each as mutable or immutable: list, dict, set, int, str, tuple, frozenset.

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