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Python Mutability (programming.dev)
submitted 1 year ago by to c/python@programming.dev
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An exercise to help build the right mental model for Python data. The “Solution” link uses memory_graph to visualize execution and reveals what’s actually happening:

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[–] 3 points 1 year ago (3 children)

It's always fun to guess whether python will call __add__ or __iadd__.

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  • [–] [S] 3 points 1 year ago (2 children)

    __add__ is called with + and __iadd__ is called with +=, and there is a difference: https://www.reddit.com/r/PythonLearning/comments/1nw08wu/right_mental_model_for_python_data/

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  • [–] 3 points 1 year ago* (1 child)

    Except if __iadd__ doesn't exist on the type, then __add__ is called. The variable is always reassigned. Quick example:

    x = (0, [1, 2])
try:
    x[1] += [3]  # calls list.__iadd__, then reassigns x[1]
except TypeError as e:
    print(e)

x += (4,)  # calls tuple.__add__, then reassigns x

print(x)

    What is printed?

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  • [–] [S] 1 point 1 year ago
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    • [–] 1 point 1 year ago (1 child)

    I so wonder what a will result in.

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