attributeError：键入对象＆＃x27; filepath＆＃x27;没有属性＆＃x27; _flavour＆＃x27; [pydantic]

Question

我使用pydantic进行数据验证。我想做的是创建一个具有可选字段的模型，该模型指向现有文件。问题是，下面的代码不起作用。

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'

有解决方法吗？

编辑：Python版本为3.9.8，Pydantic版本为1.9.0。

Answer 1

我认为您需要将默认值作为字符串提供：

from pydantic import BaseModel, FilePath


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


model = Model()

edit：pydantic似乎没有检查默认值是存在的文件：

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')

但是它确实检查了是否提供：

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：这是预期的行为，如果您想要此检查，可以使用config.validate_all = true = 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)