Iterator vs Generator — What’s the Difference?

Iterators and generators are closely related and often used together, they are not the same. Let’s break it down clearly. Aspect Iterator Generator Definition Any object that implements the iterator protocol (iter() and next() in Python, or .next() in JavaScript). A special type of iterator that yields values using yield or yield*, often created with less boilerplate. Creation Manually implemented by defining a class (Python) or an object with .next() (JavaScript). Automatically created when a function contains yield. Syntax Verbose, needs boilerplate code. Concise and easy to write. Memory Can be optimized if implemented carefully. Always lazy (values are produced one at a time, on demand). Use Case When you need more control over the iteration protocol. When you want to produce a sequence lazily with simpler syntax.

May 1, 2025 - 17:37

Iterators and generators are closely related and often used together, they are not the same. Let’s break it down clearly.

Aspect	Iterator	Generator
Definition	Any object that implements the iterator protocol (`__iter__()` and `__next__()` in Python, or `.next()` in JavaScript).	A special type of iterator that yields values using `yield` or `yield*`, often created with less boilerplate.
Creation	Manually implemented by defining a class (Python) or an object with `.next()` (JavaScript).	Automatically created when a function contains `yield`.
Syntax	Verbose, needs boilerplate code.	Concise and easy to write.
Memory	Can be optimized if implemented carefully.	Always lazy (values are produced one at a time, on demand).
Use Case	When you need more control over the iteration protocol.	When you want to produce a sequence lazily with simpler syntax.