Reference library

Comprehensions & generators

List/dict/set comprehensions, generator expressions, and lazy iteration.

4 matches

How to Send Values into a Python Generator Coroutine

Use the .send() method to pass values into a running generator coroutine and capture them.

def coroutine():
    received = []
    while True:
        value = yield
        received.append(value)
        print(f"Coroutine received: {value}")
        if value == "stop":
            break
    return received

if __name__ == "__main__":
    gen = coroutine()
    next(gen)  # Prime the generator
    gen.send("he…

13 0 Open

Comprehensions & generators medium

How to Throw an Exception into a Python Generator

This code demonstrates how to use the .throw() method on a generator to inject an exception at its current yield point and let it recover gracefully.

generator throw exception

Python

def demo_throw_into_generator():
    """Demonstrate throwing an exception into a running generator."""
    def counter():
        """Generator that counts until interrupted."""
        try:
            i = 0
            while True:
                yield i
                i += 1
        except ValueError as e:
        …

12 0 Open

Comprehensions & generators medium

How to stream parse JSON arrays in Python

This code demonstrates two generators: one that streams a JSON array as individual chunks, and another that incrementally parses those chunks into Python objects using json.JSONDecoder.

json generator streaming

Python

import json


def json_array_stream(items):
    """Generator that yields JSON-encoded values one at a time."""
    yield "["
    for i, item in enumerate(items):
        if i > 0:
            yield ","
        yield json.dumps(item)
    yield "]"


def parse_json_stream(stream):
    """Consumes a stream of JSON fragme…

14 0 Open

Comprehensions & generators medium

Merge Sorted Iterators with a Heap Generator in Python

Merge multiple sorted iterators into a single sorted stream using a heap and generator, yielding values lazily in order.

heapq generator merge

Python

import heapq

def merge_sorted_iterators(*iterators):
    heap = []
    for idx, iterator in enumerate(iterators):
        try:
            value = next(iterator)
            heapq.heappush(heap, (value, idx, iterator))
        except StopIteration:
            continue

    while heap:
        value, idx, iterator = …

15 0 Open

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