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 filter a generator with a predicate function in Python

This code defines a generator function that yields only items from an iterable that satisfy a given predicate, then tests it with even and positive number filters.

generators filtering lazy evaluation

Python

def filter_gen(predicate, iterable):
    for item in iterable:
        if predicate(item):
            yield item

def is_even(num):
    return num % 2 == 0

def is_positive(num):
    return num > 0

if __name__ == "__main__":
    numbers = range(-5, 10)
    
    even_numbers = list(filter_gen(is_even, numbers))
    p…

10 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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