3 snippets across 2 stacks - Python, JavaScript
Also written as yield from
def gen():
yield valuedef 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))3
2
1
1000000Note Generators produce values lazily, consuming almost no memory regardless of size. They are single-use: once exhausted, they cannot be restarted.
yield from iterabledef flatten(nested):
for item in nested:
if isinstance(item, list):
yield from flatten(item)
else:
yield item
data = [1, [2, [3, 4]], [5, 6]]
print(list(flatten(data)))[1, 2, 3, 4, 5, 6]Note yield from delegates to a sub-generator and passes values through. It handles send() and throw() transparently, unlike a manual for-loop with yield.
function* name() { yield value; }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); // 102Note Generators are lazy -- they produce values on demand. Execution pauses at each yield and resumes when next() is called.