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Python Number and Truthiness Gotchas: Banker's Rounding, Floor Division, is vs ==, 0.1+0.2 and Empty Values

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Self-Hosting & Infra beginner 5 min read $0.01 Updated 2026-10-20

Executed on Python 3.10: float addition, round-half-even, floor division with negatives, modulo sign, int truncation, truthiness of empty containers and strings, is versus == on literals and lists, and mutable list copies.

round(2.5) is 2, -7 // 2 is -4, "0" is truthy and None == False is False. Check each result, learn why, and use Decimal, math functions and explicit checks to get the behavior you intended.

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