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How to Implement takewhile Generator in Python
A generator that yields items from an iterable until a condition fails, like itertools.takewhile.
def takewhile(predicate, iterable):
for item in iterable:
if not predicate(item):
break
yield item
if __name__ == "__main__":
numbers = [1, 2, 3, 4, 5, 1, 2, 3]
result = list(takewhile(lambda x: x < 4, numbers))
print(result)How to Implement the Iterator Protocol in Python
A manual iterator class using __iter__ and __next__, compared with an equivalent generator using yield.
class ManualCounter:
def __init__(self, limit):
self.limit = limit
self.current = 0
def __iter__(self):
return self
def __next__(self):
if self.current >= self.limit:
raise StopIteration
value = self.current
self.current += 1
return valu…How to Merge Multiple Iterables with a Generator in Python
This code defines a generator function that 'chains' or merges multiple iterables into a single iterator, which is then converted to a list.
def chain(*iterables):
for iterable in iterables:
yield from iterable
def main():
list1 = [1, 2, 3]
tuple1 = (4, 5)
set1 = {6, 7}
string1 = "89"
result = list(chain(list1, tuple1, set1, string1))
print(result)
if __name__ == "__main__":
main()How to Parse CSV Rows as Generator Dicts in Python
Reads a CSV file and yields each row as a dictionary one at a time using a generator, so the file is processed lazily.
import csv
from pathlib import Path
def csv_to_dicts(filepath):
with open(filepath, mode="r", newline="", encoding="utf-8") as file:
reader = csv.DictReader(file)
for row in reader:
yield row
if __name__ == "__main__":
sample_csv = Path("sample_data.csv")
sample_csv.write_text…How to Repeat a Generator Cycle Single Value in Python
Build a generator that repeats a single value across multiple cycles, each cycle adding an extra repetition to mark its completion.
def repeat_with_cycle(value, cycle_limit, repetitions):
"""
Repeats a single value until reaching a cycle limit,
then yields the value one more time to demonstrate a full cycle.
Args:
value: The single value to repeat.
cycle_limit: Number of repetitions per cycle.
repetitio…How to Use Comprehensions and Generators in Python
Demonstrate list, set, and dictionary comprehensions plus generator expressions and generator functions in one beginner-friendly script.
def demonstrate_comprehensions_generators():
# List comprehension: transform and filter in one line
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
squares = [num ** 2 for num in numbers if num % 2 == 0]
print(f"Square of even numbers (list comprehension): {squares}")
# Set comprehension: unique values
…How to skip items until a condition is met in Python
Use itertools.dropwhile to skip leading elements while a predicate returns true, then yield the rest of the sequence unchanged.
def is_negative(x):
return x < 0
numbers = [-3, -1, 0, 5, 2, -8, 7]
result = list(itertools.dropwhile(is_negative, numbers))
print(f"Original: {numbers}")
print(f"After dropwhile: {result}")Python Generator to Filter Duplicates with a Seen Set
A lazily-evaluated generator function that yields only the first occurrence of each item, using a set to track seen values.
def unique_generator(items):
seen = set()
for item in items:
if item not in seen:
seen.add(item)
yield item
if __name__ == "__main__":
data = [1, 2, 2, 3, 3, 3, 4, 5, 5]
result = list(unique_generator(data))
print(result)How to Stream Tokens from a Mock LLM in Python
Simulate real-time LLM streaming by yielding tokens one at a time with a delay, making it easy to test streaming UIs.
import time
from typing import Generator
def stream_tokens(text: str, delay: float = 0.05) -> Generator[str, None, None]:
"""Simulate an LLM streaming tokens word by word."""
for word in text.split():
yield word
time.sleep(delay)
if __name__ == "__main__":
sample = "Hello world! This is…How to Paginate a List with a Generator in Python
Define a generator that yields list items in fixed-size pages, simulating pagination for cloud resource APIs.
from typing import List, Iterator
def paginate_generator(items: List[str], page_size: int = 3) -> Iterator[List[str]]:
"""Yield items in fixed-size chunks with a mock pagination pattern."""
for i in range(0, len(items), page_size):
yield items[i:i + page_size]
if __name__ == "__main__":
resources…asyncio sleep cooperative scheduling demo in Python
This demo shows how asyncio.sleep yields control between concurrent tasks, letting multiple workers interleave their ticks.
import asyncio
async def worker(name, delay):
for i in range(3):
print(f"{name}: tick {i}")
await asyncio.sleep(delay)
return f"{name} done"
async def main():
tasks = [
asyncio.create_task(worker("A", 0.1)),
asyncio.create_task(worker("B", 0.2)),
asyncio.create_tas…Browse by section
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