# Copyright 2019-2021 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""
This module is to read data from MindRecord.
"""
import platform
from .shardreader import ShardReader
from .shardheader import ShardHeader
from .shardutils import populate_data
from .shardutils import check_parameter
from .common.exceptions import ParamTypeError
__all__ = ['FileReader']
[docs]class FileReader:
"""
Class to read MindRecord files.
Note:
If `file_name` is a file path, it tries to load all MindRecord files generated \
in a conversion, and throws an exception if a MindRecord file is missing.
If `file_name` is file path list, only the MindRecord files in the list are loaded.
Args:
file_name (str, list[str]): One of MindRecord file path or file path list.
num_consumer (int, optional): Number of reader workers which load data. Default: 4.
It should not be smaller than 1 or larger than the number of processor cores.
columns (list[str], optional): A list of fields where corresponding data would be read. Default: None.
operator (int, optional): Reserved parameter for operators. Default: None.
Raises:
ParamValueError: If `file_name`, `num_consumer` or `columns` is invalid.
Examples:
>>> from mindspore.mindrecord import FileReader
>>>
>>> mindrecord_file = "/path/to/mindrecord/file"
>>> reader = FileReader(file_name=mindrecord_file)
>>>
>>> # create iterator for mindrecord and get saved data
>>> for _, item in enumerate(reader.get_next()):
... ori_data = item
>>> reader.close()
"""
@check_parameter
def __init__(self, file_name, num_consumer=4, columns=None, operator=None):
if columns:
if isinstance(columns, list):
self._columns = columns
else:
raise ParamTypeError('columns', 'list')
else:
self._columns = None
self._reader = ShardReader()
self._file_name = ""
if platform.system().lower() == "windows":
if isinstance(file_name, list):
self._file_name = [item.replace("\\", "/") for item in file_name]
else:
self._file_name = file_name.replace("\\", "/")
else:
self._file_name = file_name
self._reader.open(self._file_name, num_consumer, columns, operator)
self._header = ShardHeader(self._reader.get_header())
self._reader.launch()
[docs] def get_next(self):
"""
Yield a batch of data according to columns at a time.
Returns:
dict, a batch whose keys are the same as columns.
Raises:
MRMUnsupportedSchemaError: If schema is invalid.
"""
iterator = self._reader.get_next()
while iterator:
for blob, raw in iterator:
yield populate_data(raw, blob, self._columns, self._header.blob_fields, self._header.schema)
iterator = self._reader.get_next()
[docs] def close(self):
"""Stop reader worker and close file."""
self._reader.close()