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# 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.
"""Convert from Python type names to sqlite3 column types"""
from __future__ import print_function, division, absolute_import
import numpy as np
_dtype_to_db_type_dict = {
'int': 'INT',
'int8': 'INT',
'int16': 'INT',
'int32': 'INT',
'int64': 'INT',
'uint8': 'INT',
'uint16': 'INT',
'uint32': 'INT',
'uint64': 'INT',
'bool': 'INT',
'float': 'FLOAT',
'float32': 'FLOAT',
'float64': 'FLOAT',
'object': 'TEXT',
'object_': 'TEXT',
'string_': 'TEXT',
'str': 'TEXT',
'category': 'TEXT',
}
def _lookup_type_name(type_name):
if type_name in _dtype_to_db_type_dict:
return _dtype_to_db_type_dict[type_name]
else:
return None
def _candidate_type_names(python_type_representation):
"""Generator which yields possible type names to look up in the conversion
dictionary.
Parameters
----------
python_type_representation : object
Any Python object which represents a type, such as `int`,
`dtype('int8')`, `np.int8`, or `"int8"`.
"""
# if we get a dtype object i.e. dtype('int16'), then pull out its name
if hasattr(python_type_representation, 'name'):
yield python_type_representation.name
# convert Python types by adding their type's name
if hasattr(python_type_representation, '__name__'):
yield python_type_representation.__name__
# for a dtype like dtype('S3') need to access dtype.type.__name__
# to get 'string_'
if hasattr(python_type_representation, 'type'):
if hasattr(python_type_representation.type, '__name__'):
yield python_type_representation.type.__name__
yield str(python_type_representation)
def db_type(python_type_representation):
"""
Converts from any of:
(1) Python type
(2) NumPy/Pandas dtypes
(3) string names of types
...to a sqlite3 type name
"""
for type_name in _candidate_type_names(python_type_representation):
db_type_name = _lookup_type_name(type_name)
if db_type_name:
return db_type_name
raise ValueError("Failed to find sqlite3 column type for %s" % (
python_type_representation))
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