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5 posts · blog.lerner.co.il
Reuven Lerner is formally announcing his one-on-one Python coaching sessions, which have been offered informally for years. These sessions cover code review, architecture, Git issues, pair programming, and career advice, providing private, recorded help for $300 per hour.
The post explains that np.nan is a special floating‑point value that propagates through arithmetic and never compares equal, even to itself. It shows how this breaks naïve equality checks in pandas and suggests using pandas' isna/notna utilities instead.
A callable in Python is any object that implements `__call__`. The post shows a minimal class with `__call__` and notes that the built‑in `callable()` checks for that method.
A short blog post showing that Python's `+=` operator invokes `__add__` and rebinds the left‑hand variable to a new object rather than mutating it in place.
The post explains that Python’s `in` operator first looks for a `__contains__` method on the object and uses its boolean result; if absent it falls back to iterating via `__iter__`. Implementing `__contains__` can make membership checks faster, especially for large collections, by avoiding full iteration.
