369 lines
10 KiB
Python
369 lines
10 KiB
Python
"""
|
|
Table Schema builders
|
|
|
|
https://specs.frictionlessdata.io/json-table-schema/
|
|
"""
|
|
from __future__ import annotations
|
|
|
|
from typing import (
|
|
TYPE_CHECKING,
|
|
Any,
|
|
cast,
|
|
)
|
|
import warnings
|
|
|
|
import pandas._libs.json as json
|
|
from pandas._typing import (
|
|
DtypeObj,
|
|
JSONSerializable,
|
|
)
|
|
|
|
from pandas.core.dtypes.base import _registry as registry
|
|
from pandas.core.dtypes.common import (
|
|
is_bool_dtype,
|
|
is_categorical_dtype,
|
|
is_datetime64_dtype,
|
|
is_datetime64tz_dtype,
|
|
is_extension_array_dtype,
|
|
is_integer_dtype,
|
|
is_numeric_dtype,
|
|
is_period_dtype,
|
|
is_string_dtype,
|
|
is_timedelta64_dtype,
|
|
)
|
|
from pandas.core.dtypes.dtypes import CategoricalDtype
|
|
|
|
from pandas import DataFrame
|
|
import pandas.core.common as com
|
|
|
|
if TYPE_CHECKING:
|
|
from pandas import Series
|
|
from pandas.core.indexes.multi import MultiIndex
|
|
|
|
loads = json.loads
|
|
|
|
TABLE_SCHEMA_VERSION = "1.4.0"
|
|
|
|
|
|
def as_json_table_type(x: DtypeObj) -> str:
|
|
"""
|
|
Convert a NumPy / pandas type to its corresponding json_table.
|
|
|
|
Parameters
|
|
----------
|
|
x : np.dtype or ExtensionDtype
|
|
|
|
Returns
|
|
-------
|
|
str
|
|
the Table Schema data types
|
|
|
|
Notes
|
|
-----
|
|
This table shows the relationship between NumPy / pandas dtypes,
|
|
and Table Schema dtypes.
|
|
|
|
============== =================
|
|
Pandas type Table Schema type
|
|
============== =================
|
|
int64 integer
|
|
float64 number
|
|
bool boolean
|
|
datetime64[ns] datetime
|
|
timedelta64[ns] duration
|
|
object str
|
|
categorical any
|
|
=============== =================
|
|
"""
|
|
if is_integer_dtype(x):
|
|
return "integer"
|
|
elif is_bool_dtype(x):
|
|
return "boolean"
|
|
elif is_numeric_dtype(x):
|
|
return "number"
|
|
elif is_datetime64_dtype(x) or is_datetime64tz_dtype(x) or is_period_dtype(x):
|
|
return "datetime"
|
|
elif is_timedelta64_dtype(x):
|
|
return "duration"
|
|
elif is_categorical_dtype(x):
|
|
return "any"
|
|
elif is_extension_array_dtype(x):
|
|
return "any"
|
|
elif is_string_dtype(x):
|
|
return "string"
|
|
else:
|
|
return "any"
|
|
|
|
|
|
def set_default_names(data):
|
|
"""Sets index names to 'index' for regular, or 'level_x' for Multi"""
|
|
if com.all_not_none(*data.index.names):
|
|
nms = data.index.names
|
|
if len(nms) == 1 and data.index.name == "index":
|
|
warnings.warn("Index name of 'index' is not round-trippable.")
|
|
elif len(nms) > 1 and any(x.startswith("level_") for x in nms):
|
|
warnings.warn(
|
|
"Index names beginning with 'level_' are not round-trippable."
|
|
)
|
|
return data
|
|
|
|
data = data.copy()
|
|
if data.index.nlevels > 1:
|
|
data.index.names = com.fill_missing_names(data.index.names)
|
|
else:
|
|
data.index.name = data.index.name or "index"
|
|
return data
|
|
|
|
|
|
def convert_pandas_type_to_json_field(arr):
|
|
dtype = arr.dtype
|
|
if arr.name is None:
|
|
name = "values"
|
|
else:
|
|
name = arr.name
|
|
field: dict[str, JSONSerializable] = {
|
|
"name": name,
|
|
"type": as_json_table_type(dtype),
|
|
}
|
|
|
|
if is_categorical_dtype(dtype):
|
|
cats = dtype.categories
|
|
ordered = dtype.ordered
|
|
|
|
field["constraints"] = {"enum": list(cats)}
|
|
field["ordered"] = ordered
|
|
elif is_period_dtype(dtype):
|
|
field["freq"] = dtype.freq.freqstr
|
|
elif is_datetime64tz_dtype(dtype):
|
|
field["tz"] = dtype.tz.zone
|
|
elif is_extension_array_dtype(dtype):
|
|
field["extDtype"] = dtype.name
|
|
return field
|
|
|
|
|
|
def convert_json_field_to_pandas_type(field):
|
|
"""
|
|
Converts a JSON field descriptor into its corresponding NumPy / pandas type
|
|
|
|
Parameters
|
|
----------
|
|
field
|
|
A JSON field descriptor
|
|
|
|
Returns
|
|
-------
|
|
dtype
|
|
|
|
Raises
|
|
------
|
|
ValueError
|
|
If the type of the provided field is unknown or currently unsupported
|
|
|
|
Examples
|
|
--------
|
|
>>> convert_json_field_to_pandas_type({"name": "an_int", "type": "integer"})
|
|
'int64'
|
|
|
|
>>> convert_json_field_to_pandas_type(
|
|
... {
|
|
... "name": "a_categorical",
|
|
... "type": "any",
|
|
... "constraints": {"enum": ["a", "b", "c"]},
|
|
... "ordered": True,
|
|
... }
|
|
... )
|
|
CategoricalDtype(categories=['a', 'b', 'c'], ordered=True)
|
|
|
|
>>> convert_json_field_to_pandas_type({"name": "a_datetime", "type": "datetime"})
|
|
'datetime64[ns]'
|
|
|
|
>>> convert_json_field_to_pandas_type(
|
|
... {"name": "a_datetime_with_tz", "type": "datetime", "tz": "US/Central"}
|
|
... )
|
|
'datetime64[ns, US/Central]'
|
|
"""
|
|
typ = field["type"]
|
|
if typ == "string":
|
|
return "object"
|
|
elif typ == "integer":
|
|
return "int64"
|
|
elif typ == "number":
|
|
return "float64"
|
|
elif typ == "boolean":
|
|
return "bool"
|
|
elif typ == "duration":
|
|
return "timedelta64"
|
|
elif typ == "datetime":
|
|
if field.get("tz"):
|
|
return f"datetime64[ns, {field['tz']}]"
|
|
else:
|
|
return "datetime64[ns]"
|
|
elif typ == "any":
|
|
if "constraints" in field and "ordered" in field:
|
|
return CategoricalDtype(
|
|
categories=field["constraints"]["enum"], ordered=field["ordered"]
|
|
)
|
|
elif "extDtype" in field:
|
|
return registry.find(field["extDtype"])
|
|
else:
|
|
return "object"
|
|
|
|
raise ValueError(f"Unsupported or invalid field type: {typ}")
|
|
|
|
|
|
def build_table_schema(
|
|
data: DataFrame | Series,
|
|
index: bool = True,
|
|
primary_key: bool | None = None,
|
|
version: bool = True,
|
|
) -> dict[str, JSONSerializable]:
|
|
"""
|
|
Create a Table schema from ``data``.
|
|
|
|
Parameters
|
|
----------
|
|
data : Series, DataFrame
|
|
index : bool, default True
|
|
Whether to include ``data.index`` in the schema.
|
|
primary_key : bool or None, default True
|
|
Column names to designate as the primary key.
|
|
The default `None` will set `'primaryKey'` to the index
|
|
level or levels if the index is unique.
|
|
version : bool, default True
|
|
Whether to include a field `pandas_version` with the version
|
|
of pandas that last revised the table schema. This version
|
|
can be different from the installed pandas version.
|
|
|
|
Returns
|
|
-------
|
|
schema : dict
|
|
|
|
Notes
|
|
-----
|
|
See `Table Schema
|
|
<https://pandas.pydata.org/docs/user_guide/io.html#table-schema>`__ for
|
|
conversion types.
|
|
Timedeltas as converted to ISO8601 duration format with
|
|
9 decimal places after the seconds field for nanosecond precision.
|
|
|
|
Categoricals are converted to the `any` dtype, and use the `enum` field
|
|
constraint to list the allowed values. The `ordered` attribute is included
|
|
in an `ordered` field.
|
|
|
|
Examples
|
|
--------
|
|
>>> df = pd.DataFrame(
|
|
... {'A': [1, 2, 3],
|
|
... 'B': ['a', 'b', 'c'],
|
|
... 'C': pd.date_range('2016-01-01', freq='d', periods=3),
|
|
... }, index=pd.Index(range(3), name='idx'))
|
|
>>> build_table_schema(df)
|
|
{'fields': \
|
|
[{'name': 'idx', 'type': 'integer'}, \
|
|
{'name': 'A', 'type': 'integer'}, \
|
|
{'name': 'B', 'type': 'string'}, \
|
|
{'name': 'C', 'type': 'datetime'}], \
|
|
'primaryKey': ['idx'], \
|
|
'pandas_version': '1.4.0'}
|
|
"""
|
|
if index is True:
|
|
data = set_default_names(data)
|
|
|
|
schema: dict[str, Any] = {}
|
|
fields = []
|
|
|
|
if index:
|
|
if data.index.nlevels > 1:
|
|
data.index = cast("MultiIndex", data.index)
|
|
for level, name in zip(data.index.levels, data.index.names):
|
|
new_field = convert_pandas_type_to_json_field(level)
|
|
new_field["name"] = name
|
|
fields.append(new_field)
|
|
else:
|
|
fields.append(convert_pandas_type_to_json_field(data.index))
|
|
|
|
if data.ndim > 1:
|
|
for column, s in data.items():
|
|
fields.append(convert_pandas_type_to_json_field(s))
|
|
else:
|
|
fields.append(convert_pandas_type_to_json_field(data))
|
|
|
|
schema["fields"] = fields
|
|
if index and data.index.is_unique and primary_key is None:
|
|
if data.index.nlevels == 1:
|
|
schema["primaryKey"] = [data.index.name]
|
|
else:
|
|
schema["primaryKey"] = data.index.names
|
|
elif primary_key is not None:
|
|
schema["primaryKey"] = primary_key
|
|
|
|
if version:
|
|
schema["pandas_version"] = TABLE_SCHEMA_VERSION
|
|
return schema
|
|
|
|
|
|
def parse_table_schema(json, precise_float):
|
|
"""
|
|
Builds a DataFrame from a given schema
|
|
|
|
Parameters
|
|
----------
|
|
json :
|
|
A JSON table schema
|
|
precise_float : bool
|
|
Flag controlling precision when decoding string to double values, as
|
|
dictated by ``read_json``
|
|
|
|
Returns
|
|
-------
|
|
df : DataFrame
|
|
|
|
Raises
|
|
------
|
|
NotImplementedError
|
|
If the JSON table schema contains either timezone or timedelta data
|
|
|
|
Notes
|
|
-----
|
|
Because :func:`DataFrame.to_json` uses the string 'index' to denote a
|
|
name-less :class:`Index`, this function sets the name of the returned
|
|
:class:`DataFrame` to ``None`` when said string is encountered with a
|
|
normal :class:`Index`. For a :class:`MultiIndex`, the same limitation
|
|
applies to any strings beginning with 'level_'. Therefore, an
|
|
:class:`Index` name of 'index' and :class:`MultiIndex` names starting
|
|
with 'level_' are not supported.
|
|
|
|
See Also
|
|
--------
|
|
build_table_schema : Inverse function.
|
|
pandas.read_json
|
|
"""
|
|
table = loads(json, precise_float=precise_float)
|
|
col_order = [field["name"] for field in table["schema"]["fields"]]
|
|
df = DataFrame(table["data"], columns=col_order)[col_order]
|
|
|
|
dtypes = {
|
|
field["name"]: convert_json_field_to_pandas_type(field)
|
|
for field in table["schema"]["fields"]
|
|
}
|
|
|
|
# No ISO constructor for Timedelta as of yet, so need to raise
|
|
if "timedelta64" in dtypes.values():
|
|
raise NotImplementedError(
|
|
'table="orient" can not yet read ISO-formatted Timedelta data'
|
|
)
|
|
|
|
df = df.astype(dtypes)
|
|
|
|
if "primaryKey" in table["schema"]:
|
|
df = df.set_index(table["schema"]["primaryKey"])
|
|
if len(df.index.names) == 1:
|
|
if df.index.name == "index":
|
|
df.index.name = None
|
|
else:
|
|
df.index.names = [
|
|
None if x.startswith("level_") else x for x in df.index.names
|
|
]
|
|
|
|
return df
|