Blog
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Python operator overloading: The arithmetic magic methods
Just as + in Python invokes __add__, other operators invoke other magic methods: • – is __sub__• * is __mul__• / is __truediv__• // is __floordiv__• % is __mod__• ** is __pow__ Your methods can do whatever you want. But do try to stick to conventional expectations.
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Claude Code always produces something. That’s the hard part.
I’ve been using Claude Code several hours a day for months, and I’m having a blast. But an agent does what you tell it, not what you meant — which is why validating your results now matters more than the results themselves.
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Python’s __radd__: How reflected operators handle 5 + x
If you tell Python it’ll run x.__add__(5), which handles the int 5. But what about int.__add__ doesn’t know how to handle x. So it returns NotImplemented — and Python turns it around, calling: That’s the “reverse add” magic method!
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Python `__add__`: Return a new instance, not an int
If your Python class implements __add__, it should usually return a new instance of your class, not an int:
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Python operator overloading: Implementing __add__ for +
How can your Python object support +? Implement __add__:
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Python operator overloading: Why x + y and y + x give different errors
Operators in Python are turned into “magic” method calls: x + y # becomes x.__add__(y) So: Different errors from different methods!
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Mutable default arguments in Python: why `__defaults__` bites
Because Python functions’ defaults are kept in __defaults__, avoid mutable defaults: add1.__defaults__ # ([1, 1, 1],)
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Python generator frames: Inspecting locals with gi_frame
When a Python generator yields, its stack frame remains — inspect it for the current line and local variables:
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MIT just called for an educational revolution
As someone who teaches Python programming for a living, I’ve spent the last few years wrestling with the educational implications of AI. I’m changing everything I do to adjust to our new AI reality, experimenting with new ideas, including my AI-based Socratic tutor (https://practice.lernerpython.com/). I keep what works, throw away what doesn’t, and then try…
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AI seminars — just one of the big changes at LernerPython
July and August are often when people take a break or go on vacation. But for me, this summer has been super busy, full of writing and improving LernerPython based on feedback I’ve gotten from people around the world. And so, I’m here with some big changes I’m making at LernerPython World Headquarters: 1. AI…