Why Python Dictionary Keys Overwrite Each Other: Hashing, Equality & Identity

This article explores three Python quirks: how dictionary keys with equal numeric values overwrite each other due to hashing and equality rules, why a return statement inside a try block is superseded by a return in the finally clause, and how object identity and id values behave, including hash collisions and memory reuse.

Exception HandlingHashingPython

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Why Python Dictionary Keys Overwrite Each Other: Hashing, Equality & Identity

Raymond Ops

Apr 25, 2025 · Fundamentals

Understanding Python’s `is` Operator, re.sub quirks, and list pitfalls

This article explains why Python’s `is` operator yields True or False for integers, how integer caching and code‑block scope affect object identity, uncovers a subtle misuse of re.sub’s count parameter, clarifies lstrip’s character‑wise stripping, and demonstrates the pitfalls of creating nested lists with the `[*] * n` syntax.

PythonString Manipulationlist-issues

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Understanding Python’s `is` Operator, re.sub quirks, and list pitfalls

MaGe Linux Operations

Feb 8, 2021 · Fundamentals

Why Python Overwrites Dict Entries with 5 vs 5.0 and Other Hidden Behaviors

This article explores three surprising Python quirks: how numeric keys like 5 and 5.0 collide in dictionaries, why a return statement in a finally block overrides earlier returns, and how object identity and hash values can behave unexpectedly, revealing the language’s underlying mechanics.

Hashdictionaryobject-identity

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Why Python Overwrites Dict Entries with 5 vs 5.0 and Other Hidden Behaviors

Python Programming Learning Circle

Apr 9, 2020 · Fundamentals

Understanding the Difference Between Python's `is` and `==` Operators and Integer Caching

The article explains how Python's `is` operator checks object identity while `==` checks value equality, illustrates the small‑integer caching mechanism that makes integers from -5 to 256 share the same object, and shows how assignment patterns affect identity results.

identityinteger cachingis-operator

0 likes · 4 min read

Understanding the Difference Between Python's `is` and `==` Operators and Integer Caching