AttributeError: type object 'FilePath' has no attribute '_flavour' [pydantic]

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I use pydantic for data validation. What I want to do is to create a model with an optional field, which points to the existing file. The problem is, the code below does not work.

from pydantic import BaseModel, FilePath


class Model(BaseModel):
    # Assuming I have file.txt in working directory.
    file: FilePath = FilePath('./file.txt')


model = Model()

Traceback (most recent call last):
  File "C:\Users\mikheenkov\temp.py", line 4, in <module>
    class Model(BaseModel):
  File "C:\Users\mikheenkov\temp.py", line 5, in Model
    ssh_server_host_key: FilePath = FilePath('.')
  File "C:\Program Files\Python39\lib\pathlib.py", line 1082, in __new__
    self = cls._from_parts(args, init=False)
  File "C:\Program Files\Python39\lib\pathlib.py", line 707, in _from_parts
    drv, root, parts = self._parse_args(args)
  File "C:\Program Files\Python39\lib\pathlib.py", line 700, in _parse_args
    return cls._flavour.parse_parts(parts)
AttributeError: type object 'FilePath' has no attribute '_flavour'

Is there a workaround?

EDIT: Python version is 3.9.8 and pydantic version is 1.9.0.

pydantic python
1 Answers

I think that you need to provide the default value as a string:

from pydantic import BaseModel, FilePath


class Model(BaseModel):
    # Assuming I have file.txt in working directory.
    file: FilePath = './file.txt'


model = Model()

EDIT: pydantic does not seem to check that the default value is a file that exists:

In [18]: class Model(BaseModel):
    ...:     # Assuming no_such_file.txt does not exist
    ...:     file: FilePath = './no_such_file.txt'
    ...: 

In [19]: Model()
Out[19]: Model(file='./no_such_file.txt')

But it does check if you supply it:

In [20]: Model(file="./no_such_file.txt")
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
<ipython-input-20-e6e0f3b40736> in <module>
----> 1 Model(file="./no_such_file.txt")

~/.pyenv/versions/3.8.12/envs/uc09/lib/python3.8/site-packages/pydantic/main.cpython-38-x86_64-linux-gnu.so in pydantic.main.BaseModel.__init__()

ValidationError: 1 validation error for Model
file
  file or directory at path "no_such_file.txt" does not exist (type=value_error.path.not_exists; path=no_such_file.txt)

EDIT2: This is the intended behavior, and if you want this check you can use Config.validate_all = True:


In [29]: class Model(BaseModel):
    ...:     # Assuming no_such_file.txt does not exist
    ...:     file: FilePath = './no_such_file.txt'
    ...:     class Config:
    ...:         validate_all = True
    ...: 

In [30]: model = Model()
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
<ipython-input-30-e3d397de7fe1> in <module>
----> 1 model = Model()

~/.pyenv/versions/3.8.12/envs/uc09/lib/python3.8/site-packages/pydantic/main.cpython-38-x86_64-linux-gnu.so in pydantic.main.BaseModel.__init__()

ValidationError: 1 validation error for Model
file
  file or directory at path "no_such_file.txt" does not exist (type=value_error.path.not_exists; path=no_such_file.txt)
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