Pydantic Use of __package__ in pydantic/__init_

The Fix

pip install pydantic==2.7.2

Based on closed pydantic/pydantic issue #9221 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Jump to Verify Open PR/Commit

@@ -220,145 +220,145 @@
 # A mapping of {<member name>: (package, <module name>)} defining dynamic imports
 _dynamic_imports: 'dict[str, tuple[str, str]]' = {
-    'dataclasses': (__package__, '__module__'),
+    'dataclasses': (__spec__.parent, '__module__'),
     # functional validators

repro.py

Tested in 2.5.3 -> 2.7.0
            pydantic version: 2.7.0
        pydantic-core version: 2.18.1
          pydantic-core build: profile=release pgo=true
                 install path: C:\Python311\Lib\site-packages\pydantic
               python version: 3.11.7 (tags/v3.11.7:fa7a6f2, Dec  4 2023, 19:24:49) [MSC v.1937 64 bit (AMD64)]
                     platform: Windows-10-10.0.22631-SP0
             related packages: typing_extensions-4.11.0
                       commit: unknown

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\npip install pydantic==2.7.2\nWhen NOT to use: This fix is not applicable if the code is not run from a zip file.\n\n

Why This Fix Works in Production

Trigger: Use of __package__ in pydantic/__init__.py fails if imported from zip
Mechanism: __package__ is not set when importing from a zip file, causing import failures
Why the fix works: Replaces the use of `__package__` with `__spec__.parent` in `pydantic/__init__.py` to ensure compatibility when importing from zip files. (first fixed release: 2.7.2).

Production impact:

If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.

Why This Breaks in Prod

Shows up under Python 3.9 in real deployments (not just unit tests).
__package__ is not set when importing from a zip file, causing import failures
Surfaces as: Traceback (most recent call last):\n File "<stdin>", line 1, in <module>\n File "<frozen importlib._bootstrap>", line 1055, in _handle_fromlist\n File…

Proof / Evidence

GitHub issue: #9221
Fix PR: https://github.com/pydantic/pydantic/pull/9331
First fixed release: 2.7.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.95
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.54

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“Thanks @johanandersson-tietoevrycom for reporting this issue”

@hramezani · 2024-04-18 · repro detail · source

“I'm a bit lost, please can you format your issue using markdown so I can read the code.”

@samuelcolvin · 2024-04-12 · source

“Thanks @johanandersson-tietoevrycom for helping us to reproduce the problem. I created https://github.com/pydantic/pydantic/pull/9331 to fix the problem. It would be great if you can confirm the…”

@hramezani · 2024-04-26 · source

“Hi, I am unsure of what you want me todo”

@johanandersson-tietoevrycom · 2024-04-12 · source

Failure Signature (Search String)

Use of __package__ in pydantic/__init__.py fails if imported from zip

Error Message

Stack trace

error.txt

Error Message
-------------
Traceback (most recent call last):\n  File "<stdin>", line 1, in <module>\n  File "<frozen importlib._bootstrap>", line 1055, in _handle_fromlist\n  File "c:\tmp\testpydantic\pydantic.zip\pydantic\__init__.py", line 389, in __getattr__\n  File "c:\Python39\lib\importlib\__init__.py", line 122, in import_module\n    raise TypeError(msg.format(name))

Minimal Reproduction

repro.py

Tested in 2.5.3 -> 2.7.0
            pydantic version: 2.7.0
        pydantic-core version: 2.18.1
          pydantic-core build: profile=release pgo=true
                 install path: C:\Python311\Lib\site-packages\pydantic
               python version: 3.11.7 (tags/v3.11.7:fa7a6f2, Dec  4 2023, 19:24:49) [MSC v.1937 64 bit (AMD64)]
                     platform: Windows-10-10.0.22631-SP0
             related packages: typing_extensions-4.11.0
                       commit: unknown

Environment

Python: 3.9
Pydantic: 2

What Broke

Importing Pydantic from a zip file results in import errors and application crashes.

Why It Broke

__package__ is not set when importing from a zip file, causing import failures

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install pydantic==2.7.2

When NOT to use: This fix is not applicable if the code is not run from a zip file.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/pydantic/pydantic/pull/9331

First fixed release: 2.7.2

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

This fix is not applicable if the code is not run from a zip file.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
Upgrade behind a canary and run integration tests against the canary before 100% rollout.

Version Compatibility Table

Version	Status
2.7.2	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:configuration-error Pydantic hub Pydantic best practices All hubs All clusters

Related clusters: Data consistency OpenAPI schema Serialization

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

Pydantic Use of __package__ in pydantic/__init__.py fails if imported from zip (Fix)