🐍🚀 [3.15] thread-safe iterators

Rodrigo | MathsppOct 29, 2026

October 29, 2026

🐍🚀 [3.15] thread-safe iterators

day 13 of 15 days of Python 3.15

Hey there, 👋

How is your Python 🐍 going?

In this email we’ll talk about writing and using thread-safe iterators. 🚀

See the future schedule here and links to the previous days: https://mathspp.com/python-315

Iterators are not thread-safe

Iterators are not thread-safe out of the box.

For example, generators will raise ValueError if you try to access them from one thread while another thread is running the generator already.

Python 3.15 provides the tools to work with this.

Serialising an iterator

Given an iterator, you can now create a thread-safe version of it with

import threading

it = ...  # Non-thread-safe iterator
threadsafe_it = threading.serialize_iterator(it)

Serialising all iterators from an iterator factory

If you have an “iterator factory”, like something from itertools or a generator, you can use @threading.synchronize_iterator to automatically serialise all the iterators produce.

E.g., here’s how to write a thread-safe generator:

import threading

@threading.synchronize_iterator
def my_threadsafe_generator():
    ...

The generator function my_threadsafe_generator will automatically produce thread-safe iterators.

🐍🚀 [3.15] thread-safe iterators

Iterators are not thread-safe

Serialising an iterator

Serialising all iterators from an iterator factory

Further reading