Generator

2 snippets across 2 stacks — JavaScript, Python

JSJavaScript

Generator Functions

syntax

function* name() { yield value; }

example

function* idGenerator(start = 1) {
  let id = start;
  while (true) {
    yield id++;
  }
}
const ids = idGenerator(100);
console.log(ids.next().value); // 100
console.log(ids.next().value); // 101
console.log(ids.next().value); // 102

Note Generators are lazy -- they produce values on demand. Execution pauses at each yield and resumes when next() is called.

PYPython

Generators with yield

PY · Functions

syntax

def gen():
    yield value

example

def countdown(n: int):
    while n > 0:
        yield n
        n -= 1

for tick in countdown(3):
    print(tick)

# Generators are lazy — values produced one at a time
nums = countdown(1_000_000)
print(next(nums))

output

Note Generators produce values lazily, consuming almost no memory regardless of size. They are single-use: once exhausted, they cannot be restarted.