util/slio.py

# ==========================================================
# Modified from mmcv
# ==========================================================

import json, pickle, yaml
try:
    from yaml import CLoader as Loader, CDumper as Dumper
except ImportError:
    from yaml import Loader, Dumper

from pathlib import Path
from abc import ABCMeta, abstractmethod

# ===========================
# Rigister handler
# ===========================

class BaseFileHandler(metaclass=ABCMeta):

    @abstractmethod
    def load_from_fileobj(self, file, **kwargs):
        pass

    @abstractmethod
    def dump_to_fileobj(self, obj, file, **kwargs):
        pass

    @abstractmethod
    def dump_to_str(self, obj, **kwargs):
        pass

    def load_from_path(self, filepath, mode='r', **kwargs):
        with open(filepath, mode) as f:
            return self.load_from_fileobj(f, **kwargs)

    def dump_to_path(self, obj, filepath, mode='w', **kwargs):
        with open(filepath, mode) as f:
            self.dump_to_fileobj(obj, f, **kwargs)

class JsonHandler(BaseFileHandler):

    def load_from_fileobj(self, file):
        return json.load(file)

    def dump_to_fileobj(self, obj, file, **kwargs):
        json.dump(obj, file, **kwargs)

    def dump_to_str(self, obj, **kwargs):
        return json.dumps(obj, **kwargs)

class PickleHandler(BaseFileHandler):

    def load_from_fileobj(self, file, **kwargs):
        return pickle.load(file, **kwargs)

    def load_from_path(self, filepath, **kwargs):
        return super(PickleHandler, self).load_from_path(
            filepath, mode='rb', **kwargs)

    def dump_to_str(self, obj, **kwargs):
        kwargs.setdefault('protocol', 2)
        return pickle.dumps(obj, **kwargs)

    def dump_to_fileobj(self, obj, file, **kwargs):
        kwargs.setdefault('protocol', 2)
        pickle.dump(obj, file, **kwargs)

    def dump_to_path(self, obj, filepath, **kwargs):
        super(PickleHandler, self).dump_to_path(
            obj, filepath, mode='wb', **kwargs)

class YamlHandler(BaseFileHandler):

    def load_from_fileobj(self, file, **kwargs):
        kwargs.setdefault('Loader', Loader)
        return yaml.load(file, **kwargs)

    def dump_to_fileobj(self, obj, file, **kwargs):
        kwargs.setdefault('Dumper', Dumper)
        yaml.dump(obj, file, **kwargs)

    def dump_to_str(self, obj, **kwargs):
        kwargs.setdefault('Dumper', Dumper)
        return yaml.dump(obj, **kwargs)

file_handlers = {
    'json': JsonHandler(),
    'yaml': YamlHandler(),
    'yml': YamlHandler(),
    'pickle': PickleHandler(),
    'pkl': PickleHandler()
}

# ===========================
# load and dump
# ===========================

def is_str(x):
    """Whether the input is an string instance.

    Note: This method is deprecated since python 2 is no longer supported.
    """
    return isinstance(x, str)

def slload(file, file_format=None, **kwargs):
    """Load data from json/yaml/pickle files.

    This method provides a unified api for loading data from serialized files.

    Args:
        file (str or :obj:`Path` or file-like object): Filename or a file-like
            object.
        file_format (str, optional): If not specified, the file format will be
            inferred from the file extension, otherwise use the specified one.
            Currently supported formats include "json", "yaml/yml" and
            "pickle/pkl".

    Returns:
        The content from the file.
    """
    if isinstance(file, Path):
        file = str(file)
    if file_format is None and is_str(file):
        file_format = file.split('.')[-1]
    if file_format not in file_handlers:
        raise TypeError(f'Unsupported format: {file_format}')

    handler = file_handlers[file_format]
    if is_str(file):
        obj = handler.load_from_path(file, **kwargs)
    elif hasattr(file, 'read'):
        obj = handler.load_from_fileobj(file, **kwargs)
    else:
        raise TypeError('"file" must be a filepath str or a file-object')
    return obj


def sldump(obj, file=None, file_format=None, **kwargs):
    """Dump data to json/yaml/pickle strings or files.

    This method provides a unified api for dumping data as strings or to files,
    and also supports custom arguments for each file format.

    Args:
        obj (any): The python object to be dumped.
        file (str or :obj:`Path` or file-like object, optional): If not
            specified, then the object is dump to a str, otherwise to a file
            specified by the filename or file-like object.
        file_format (str, optional): Same as :func:`load`.

    Returns:
        bool: True for success, False otherwise.
    """
    if isinstance(file, Path):
        file = str(file)
    if file_format is None:
        if is_str(file):
            file_format = file.split('.')[-1]
        elif file is None:
            raise ValueError(
                'file_format must be specified since file is None')
    if file_format not in file_handlers:
        raise TypeError(f'Unsupported format: {file_format}')

    handler = file_handlers[file_format]
    if file is None:
        return handler.dump_to_str(obj, **kwargs)
    elif is_str(file):
        handler.dump_to_path(obj, file, **kwargs)
    elif hasattr(file, 'write'):
        handler.dump_to_fileobj(obj, file, **kwargs)
    else:
        raise TypeError('"file" must be a filename str or a file-object')