Base Classes¶

BaseInferencer¶

Abstract base class for all file type inferencers.

from filetype_detector import BaseInferencer

Description¶

The BaseInferencer class provides a common interface for all inferencer implementations. It defines the abstract infer method that must be implemented by subclasses.

Class Definition¶

class BaseInferencer(ABC):
    """Abstract base class for file format inference."""

Methods¶

`infer(file_path: Union[Path, str]) -> FileType`¶

Abstract method that must be implemented by all inferencer subclasses.

Parameters:

file_path (Union[Path, str]): Path to the file whose format should be inferred. Can be a Path object or a string representing the file system path.

Returns:

FileType: A frozen dataclass holding extensions: tuple[str, ...] and mime_types: tuple[str, ...].

Raises:

NotImplementedError: If the subclass does not implement this method.

Example:

from filetype_detector import BaseInferencer, FileType
from typing import Union
from pathlib import Path

class CustomInferencer(BaseInferencer):
    def infer(self, file_path: Union[Path, str]) -> FileType:
        # Custom implementation
        return FileType.from_extension(".custom")

Creating Custom Inferencers¶

To create a custom inferencer, subclass BaseInferencer and implement the infer method:

from filetype_detector import BaseInferencer, FileType
from typing import Union
from pathlib import Path

class MyCustomInferencer(BaseInferencer):
    """Custom inferencer implementation."""

    def infer(self, file_path: Union[Path, str]) -> FileType:
        """Infer file type using custom logic."""
        path_obj = Path(file_path)

        if path_obj.exists():
            size = path_obj.stat().st_size
            if size == 0:
                return FileType.from_extension(".empty")
            elif size < 100:
                return FileType.from_extension(".small")

        return FileType(extensions=(), mime_types=())

Best Practices¶

Validate Input: Always validate that the file exists and is accessible
Handle Errors: Raise appropriate exceptions (FileNotFoundError, ValueError, etc.)
Return FileType: Use FileType.from_extension(ext) or FileType.from_mimetype(mime) for correct MIME resolution
Type Hints: Use proper type hints for better IDE support
Documentation: Provide clear docstrings following numpy-style format