Values, types, and variables

Names point at objects

A Python variable is a name bound to an object, not a box holding a value. Assigning one name to another binds both to the same object, which is invisible for numbers and strings and very visible for lists.

That distinction is the source of the classic beginner surprise: appending to a list through one name changes what the other name sees, because there was only ever one list.

Immutable types — numbers, strings, tuples — sidestep the problem entirely. Any operation that looks like a change produces a new object instead.