🐍🚀 [3.15] 4 upgrades to the std library

October 28, 2026

🐍🚀 [3.15] 4 upgrades to the std library

day 12 of 15 days of Python 3.15

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

New object_hook in json.load

The new parameter can be set to a function.

This function runs whenever JSON loads a dictionary.

Use it with frozendict and array_hook=tuple to load JSON data as immutable:

import json

def load_immutable_json(filepath):
    with open(filepath, "r") as f:
        data = json.load(
            f,
            object_hook=frozendict,
            array_hook=tuple,
        )
    return data

New module math.integer

This new module has 6 functions that operate on integers and return integers:

1. comb(n, k)

2. perm(n, k=None)

3. gcd(*integers)

4. lcm(*integers)

5. isqrt(n)

6. factorial(n)

New re.prefixmatch function

This actually isn’t new functionality.

prefixmatch is exactly the same as match.

The problem is that match has a confusing name.

I always use it thinking it’s the same as re.search.

So, prefixmatch makes the behaviour more clear.

New code should use prefixmatch but match will be kept for backwards-compatibility.

New TaskGroup.cancel method

You can now cancel task groups (and all their tasks) with the method cancel.

Much more convenient than keeping track of all tasks manually and then cancelling each in turn.

Other exciting additions to the std library

Of course the std library got other exciting additions, but we covered many of them already:

• new built-in frozendict

• new built-in sentinel

• new module profiling and the new profiler Tachyon (profiling.sampling)

• improvements to typing (better TypedDict, new TypeForm, new @disjoint_base, ...)

Further reading

You can learn more about each new feature by reading the full article here: https://mathspp.com/blog/4-upgrades-to-the-python-standard-library-in-315

Tomorrow you’ll learn about the improvements made to iterators so they work with concurrency.

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

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