"ValueError: 'not' is not a valid parameter name" on python 3.11

[koviubi56]

First Check

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Example Code

import fastapi

app = fastapi.FastAPI()


@app.get("/")
def index():
    return {"message": "Hello World"}

Description

In Python 3.11 (Python 3.11.0b3 (main, Jun 1 2022, 13:29:14) [MSC v.1932 64 bit (AMD64)]), importing fastapi raises an exception: ValueError: 'not' is not a valid parameter name. (Running the file in Python 3.10, 3.9, and 3.8 works as expected)

Traceback

Running the file

Traceback (most recent call last):
  File "C:\Users\Tibi\Documents\example.py", line 1, in 
    import fastapi
    ^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\__init__.py", line 7, in 
    from .applications import FastAPI as FastAPI
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\applications.py", line 15, in 
    from fastapi import routing
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\routing.py", line 23, in 
    from fastapi.dependencies.models import Dependant
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\dependencies\models.py", line 3, in 
    from fastapi.security.base import SecurityBase
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\security\__init__.py", line 1, in 
    from .api_key import APIKeyCookie as APIKeyCookie
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\security\api_key.py", line 3, in 
    from fastapi.openapi.models import APIKey, APIKeyIn
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\openapi\models.py", line 103, in 
    class Schema(BaseModel):
    ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\pydantic\main.py", line 292, in __new__
    cls.__signature__ = ClassAttribute('__signature__', generate_model_signature(cls.__init__, fields, config))
                                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\pydantic\utils.py", line 258, in generate_model_signature
    merged_params[param_name] = Parameter(
                                ^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\inspect.py", line 2715, in __init__
    raise ValueError('{!r} is not a valid parameter name'.format(name))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: 'not' is not a valid parameter name

Using uvicorn

Traceback (most recent call last):
  File "", line 198, in _run_module_as_main
  File "", line 88, in _run_code
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\uvicorn\__main__.py", line 4, in 
    uvicorn.main()
    ^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\click\core.py", line 1128, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\click\core.py", line 1053, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\click\core.py", line 1395, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\click\core.py", line 754, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\uvicorn\main.py", line 437, in main
    run(app, **kwargs)
    ^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\uvicorn\main.py", line 463, in run
    server.run()
    ^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\uvicorn\server.py", line 60, in run
    return asyncio.run(self.serve(sockets=sockets))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 181, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 115, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 650, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\uvicorn\server.py", line 67, in serve
    config.load()
    ^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\uvicorn\config.py", line 458, in load
    self.loaded_app = import_from_string(self.app)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\uvicorn\importer.py", line 21, in import_from_string
    module = importlib.import_module(module_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "", line 1206, in _gcd_import
  File "", line 1178, in _find_and_load
  File "", line 1149, in _find_and_load_unlocked
  File "", line 690, in _load_unlocked
  File "", line 939, in exec_module
  File "", line 241, in _call_with_frames_removed
  File "C:\Users\Tibi\Documents\.\example.py", line 1, in 
    import fastapi
    ^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\__init__.py", line 7, in 
    from .applications import FastAPI as FastAPI
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\applications.py", line 15, in 
    from fastapi import routing
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\routing.py", line 23, in 
    from fastapi.dependencies.models import Dependant
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\dependencies\models.py", line 3, in 
    from fastapi.security.base import SecurityBase
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\security\__init__.py", line 1, in 
    from .api_key import APIKeyCookie as APIKeyCookie
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\security\api_key.py", line 3, in 
    from fastapi.openapi.models import APIKey, APIKeyIn
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\openapi\models.py", line 103, in 
    class Schema(BaseModel):
    ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\pydantic\main.py", line 292, in __new__
    cls.__signature__ = ClassAttribute('__signature__', generate_model_signature(cls.__init__, fields, config))
                                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\pydantic\utils.py", line 258, in generate_model_signature
    merged_params[param_name] = Parameter(
                                ^^^^^^^^^^
  File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\inspect.py", line 2715, in __init__
    raise ValueError('{!r} is not a valid parameter name'.format(name))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: 'not' is not a valid parameter name

The problem seems to be this line:

# File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\openapi\models.py"
class Schema(BaseModel):
    # ...
    #                                              ~~~~~~~~~~~
    not_: Optional["Schema"] = Field(default=None, alias="not")
    # ...

After changing that line to not_: Optional["Schema"] = None, there's another similar exception: ValueError: 'in' is not a valid parameter name, which is because of this:

# File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\openapi\models.py"
class Parameter(ParameterBase):
    name: str
    #                                 ~~~~~~~~~~
    in_: ParameterInType = Field(..., alias="in")

After changing that line to in_: ParameterInType, there's another similar exception: ValueError: 'in' is not a valid parameter name, which is because of this:

# File "C:\Users\Tibi\AppData\Local\Programs\Python\Python311\Lib\site-packages\fastapi\openapi\models.py"
class APIKey(SecurityBase):
    type_ = Field(SecuritySchemeType.apiKey, alias="type")
    #                          ~~~~~~~~~~
    in_: APIKeyIn = Field(..., alias="in")
    name: str

After changing that line to in_: APIKeyIn, the code works as expected.

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.78.0

Python Version

Python 3.11.0b3

Additional Context

If you would like to, I could make a PR that removes these aliases.

[alexfromapex]

Having the same issue on ARM-64 MacOS with Python 3.11.0b3

Traceback (most recent call last):
  File "/Users/alex/Code/Python/Flashcard/main.py", line 1, in <module>
    from fastapi import FastAPI
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/fastapi/__init__.py", line 7, in <module>
    from .applications import FastAPI as FastAPI
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/fastapi/applications.py", line 15, in <module>
    from fastapi import routing
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/fastapi/routing.py", line 23, in <module>
    from fastapi.dependencies.models import Dependant
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/fastapi/dependencies/models.py", line 3, in <module>
    from fastapi.security.base import SecurityBase
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/fastapi/security/__init__.py", line 1, in <module>
    from .api_key import APIKeyCookie as APIKeyCookie
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/fastapi/security/api_key.py", line 3, in <module>
    from fastapi.openapi.models import APIKey, APIKeyIn
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/fastapi/openapi/models.py", line 103, in <module>
    class Schema(BaseModel):
    ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/pydantic/main.py", line 292, in __new__
    cls.__signature__ = ClassAttribute('__signature__', generate_model_signature(cls.__init__, fields, config))
                                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/envs/notecards/lib/python3.11/site-packages/pydantic/utils.py", line 258, in generate_model_signature
    merged_params[param_name] = Parameter(
                                ^^^^^^^^^^
  File "/Users/alex/.pyenv/versions/3.11-dev/lib/python3.11/inspect.py", line 2715, in __init__
    raise ValueError('{!r} is not a valid parameter name'.format(name))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[musicinmybrain]

This seems to be related to the following issue in CPython: python/cpython#92062
The associated PR is: python/cpython#92065
A related issue in Pydantic is: pydantic/pydantic#4011
A related PR in Pydantic is: pydantic/pydantic#4012

[musicinmybrain]

The issue is still present in FastAPI 0.79.0 and Python 3.11.0b4.

[musicinmybrain]

Any thoughts on whether or not simply removing the aliases as described in the original report is an appropriate fix?

[musicinmybrain]

I found that removing the aliases as suggested leads to errors even collecting the test suite, let alone running the tests, since these aliases are used quite heavily.

[musicinmybrain]

The python-fastapi package will be retired from Fedora Linux beginning with Fedora 37 due to this issue.

[koviubi56]

This issue has been resolved in v1.10.0a1 of Pydantic.