Python Can Be Weird – Let's Look at Some Peculiar Examples

Python is a fantastic language, but sometimes it behaves in ways that make you do a double-take. Here are four classics – and the explanation behind them.

Example 1 – 8-bit problem?

CPython caches small integers from -5 to 256 as singletons. The same object is reused everywhere. Outside this range, new objects are created every time.

Example 2 – where did Ruby go?

5 == 5.0 is true, and both hash to the same value. Therefore, programming[5] = "Python" overwrites programming[5.0]. Ruby disappeared.

Example 3 – invalid syntax?

not is a unary operator with lower precedence than ==. not x == y is interpreted as not (x == y). But y == not x becomes syntactically incorrect – the parser expects an expression after ==, not an operator.

Example 4 – huh?

CPython interns short strings that look like identifiers. "wtf" becomes the same object. "wtf!" contains ! and is not considered an identifier – no interning, two different objects.

Conclusion

Python is full of such "gotchas" – and they are usually perfectly logical once you understand what's happening under the hood. Always use == for value comparison and is only when you truly mean the same object in memory.