Coverage for python/lsst/daf/butler/delegates/dataframe.py: 23%
47 statements
« prev ^ index » next coverage.py v7.2.3, created at 2023-04-19 03:42 -0700
« prev ^ index » next coverage.py v7.2.3, created at 2023-04-19 03:42 -0700
1# This file is part of daf_butler.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (http://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# This program is free software: you can redistribute it and/or modify
10# it under the terms of the GNU General Public License as published by
11# the Free Software Foundation, either version 3 of the License, or
12# (at your option) any later version.
13#
14# This program is distributed in the hope that it will be useful,
15# but WITHOUT ANY WARRANTY; without even the implied warranty of
16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17# GNU General Public License for more details.
18#
19# You should have received a copy of the GNU General Public License
20# along with this program. If not, see <http://www.gnu.org/licenses/>.
22"""Support for reading DataFrames."""
23from __future__ import annotations
25import collections.abc
26from typing import Any, Mapping, Optional
28import pandas
29import pyarrow as pa
30from lsst.daf.butler import StorageClassDelegate
31from lsst.daf.butler.formatters.parquet import DataFrameSchema
32from lsst.utils.introspection import get_full_type_name
33from lsst.utils.iteration import ensure_iterable
35from ..formatters.parquet import _standardize_multi_index_columns
37__all__ = ["DataFrameDelegate"]
40class DataFrameDelegate(StorageClassDelegate):
41 def getComponent(self, composite: pandas.DataFrame, componentName: str) -> Any:
42 """Get a component from a DataFrame.
44 Parameters
45 ----------
46 composite : `~pandas.DataFrame`
47 ``DataFrame`` to access component.
48 componentName : `str`
49 Name of component to retrieve.
51 Returns
52 -------
53 component : `object`
54 The component.
56 Raises
57 ------
58 AttributeError
59 The component can not be found.
60 """
61 if componentName == "columns":
62 if isinstance(composite.columns, pandas.MultiIndex):
63 return composite.columns
64 else:
65 return pandas.Index(self._getAllColumns(composite))
66 elif componentName == "rowcount":
67 return len(composite)
68 elif componentName == "schema":
69 return DataFrameSchema(composite.iloc[:0])
70 else:
71 raise AttributeError(
72 f"Do not know how to retrieve component {componentName} from {get_full_type_name(composite)}"
73 )
75 def handleParameters(
76 self, inMemoryDataset: pandas.DataFrame, parameters: Optional[Mapping[str, Any]] = None
77 ) -> Any:
78 """Return possibly new in-memory dataset using the supplied parameters.
80 Parameters
81 ----------
82 inMemoryDataset : `object`
83 Object to modify based on the parameters.
84 parameters : `dict`, optional
85 Parameters to apply. Values are specific to the parameter.
86 Supported parameters are defined in the associated
87 `StorageClass`. If no relevant parameters are specified the
88 ``inMemoryDataset`` will be return unchanged.
90 Returns
91 -------
92 inMemoryDataset : `object`
93 Original in-memory dataset, or updated form after parameters
94 have been used.
95 """
96 if not isinstance(inMemoryDataset, pandas.DataFrame):
97 raise ValueError(
98 "handleParameters for a DataFrame must get a DataFrame, "
99 f"not {get_full_type_name(inMemoryDataset)}."
100 )
102 if parameters is None:
103 return inMemoryDataset
105 if "columns" in parameters:
106 allColumns = self._getAllColumns(inMemoryDataset)
108 if not isinstance(parameters["columns"], collections.abc.Iterable):
109 raise NotImplementedError(
110 "InMemoryDataset of a DataFrame only supports list/tuple of string column names"
111 )
113 if isinstance(inMemoryDataset.columns, pandas.MultiIndex):
114 # We have a multi-index dataframe which needs special handling.
115 arrow_table = pa.Table.from_pandas(inMemoryDataset)
116 readColumns = _standardize_multi_index_columns(
117 arrow_table.schema,
118 parameters["columns"],
119 stringify=False,
120 )
121 else:
122 for column in ensure_iterable(parameters["columns"]):
123 if not isinstance(column, str):
124 raise NotImplementedError(
125 "InMemoryDataset of a DataFrame only supports string column names."
126 )
127 if column not in allColumns:
128 raise ValueError(f"Unrecognized column name {column!r}.")
130 # Exclude index columns from the subset.
131 readColumns = [
132 name
133 for name in ensure_iterable(parameters["columns"])
134 if name not in inMemoryDataset.index.names
135 ]
137 # Ensure uniqueness, keeping order.
138 readColumns = list(dict.fromkeys(readColumns))
140 return inMemoryDataset[readColumns]
141 else:
142 return inMemoryDataset
144 def _getAllColumns(self, inMemoryDataset: pandas.DataFrame) -> list[str]:
145 """Get all columns, including index columns.
147 Returns
148 -------
149 columns : `list` [`str`]
150 List of all columns.
151 """
152 allColumns = list(inMemoryDataset.columns)
153 if inMemoryDataset.index.names[0] is not None:
154 allColumns.extend(inMemoryDataset.index.names)
156 return allColumns