_schema.py

Go to the documentation of this file.

# This file is part of afw.
#
# Developed for the LSST Data Management System.
# This product includes software developed by the LSST Project
# (https://www.lsst.org).
# See the COPYRIGHT file at the top-level directory of this distribution
# for details of code ownership.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
__all__ = ["Key", "Field", "SchemaItem"]
 
import numpy as np
import fnmatch
import re
import collections
import astropy.units
 
import lsst.geom
from lsst.utils import continueClass, TemplateMeta
 
from ._table import _Key, _Field, _SchemaItem, Schema
 
# Objects we prefer to use over the C++ string name for
# Key/Field/SchemaItem types.
_dtypes = {
    "String": str,
    "B": np.uint8,
    "U": np.uint16,
    "I": np.int32,
    "L": np.int64,
    "F": np.float32,
    "D": np.float64,
    "Angle": lsst.geom.Angle,
}
 
 
class Key(metaclass=TemplateMeta):
    pass
 
 
class Field(metaclass=TemplateMeta):
    pass
 
 
class SchemaItem(metaclass=TemplateMeta):
    pass
 
 
def _registerInstantiations(abc, types):
    """Iterate over a private dict (filled by template instantiations in C++)
    to register template instantiations a TemplateMeta ABCs.
 
    If an entry for the type string exists in _dtypes, we use that instead of
    the string as the key, and use the string as an alias.
    """
    for k, v in types.items():
        dtype = _dtypes.get(k, None)
        if dtype is not None:
            abc.register(dtype, v)
            abc.alias(k, v)
        else:
            abc.register(k, v)
 
 
# _Key, _Field, and _SchemaItem are {str: class} dicts populated by the C++
# wrappers.  The keys are a superset of those in _dtypes.
_registerInstantiations(Key, _Key)
_registerInstantiations(Field, _Field)
_registerInstantiations(SchemaItem, _SchemaItem)
 
# Also register `float->D` as an alias; can't include
# in _dtypes because we have (and prefer) np.float64 there.
Key.alias(float, _Key["D"])
Field.alias(float, _Field["D"])
SchemaItem.alias(float, _SchemaItem["D"])
 
 
@continueClass
class Schema:  # noqa: F811
 
    def getOrderedNames(self):
        """Return a list of field names in the order the fields were added to the Schema.
 
        Returns
        -------
        names : `List`
            Field names in order they were added to the Schema.
        """
        names = []
 
        def func(item):
            names.append(item.field.getName())
        self.forEach(func)
        return names
 
    def __iter__(self):
        """Iterate over the items in the Schema.
        """
        items = []
        self.forEach(items.append)
        return iter(items)
 
    def checkUnits(self, parse_strict='raise'):
        """Check that all units in the Schema are valid Astropy unit strings.
 
        Parameters
        ----------
        parse_strict : `str`, optional
            One of 'raise' (default), 'warn', or 'strict', indicating how to
            handle unrecognized unit strings.  See also astropy.units.Unit.
        """
        def func(item):
            astropy.units.Unit(item.field.getUnits(),
                               parse_strict=parse_strict)
        self.forEach(func)
 
    def addField(self, field, type=None, doc="", units="", size=None,
                 doReplace=False, parse_strict="raise"):
        """Add a field to the Schema.
 
        Parameters
        ----------
        field : `str` or `Field`
            The string name of the Field, or a fully-constructed Field object.
            If the latter, all other arguments besides doReplace are ignored.
        type : `str`, optional
            The type of field to create.  Valid types are the keys of the
            afw.table.Field dictionary.
        doc : `str`
            Documentation for the field.
        unit : `str`
            Units for the field, or an empty string if unitless.
        size : `int`
            Size of the field; valid for string and array fields only.
        doReplace : `bool`
            If a field with this name already exists, replace it instead of
            raising pex.exceptions.InvalidParameterError.
        parse_strict : `str`
            One of 'raise' (default), 'warn', or 'strict', indicating how to
            handle unrecognized unit strings.  See also astropy.units.Unit.
 
        Returns
        -------
        result :
            Result of the `Field` addition.
        """
        if isinstance(field, str):
            field = Field[type](field, doc=doc, units=units,
                                size=size, parse_strict=parse_strict)
        return field._addTo(self, doReplace)
 
    def extract(self, *patterns, **kwargs):
        """Extract a dictionary of {<name>: <schema-item>} in which the field
        names match the given shell-style glob pattern(s).
 
        Any number of glob patterns may be passed; the result will be the
        union of all the result of each glob considered separately.
 
        Parameters
        ----------
        patterns : Array of `str`
            List of glob patterns to use to select field names.
        kwargs : `dict`
            Dictionary of additional keyword arguments.  May contain:
 
            ``regex`` : `str` or `re` pattern
                A regular expression to be used in addition to any
                glob patterns passed as positional arguments.  Note
                that this will be compared with re.match, not
                re.search.
            ``sub`` : `str`
                A replacement string (see re.MatchObject.expand) used
                to set the dictionary keys of any fields matched by
                regex.
            ``ordered`` : `bool`, optional
                If True, a collections.OrderedDict will be returned
                instead of a standard dict, with the order
                corresponding to the definition order of the
                Schema. Default is False.
 
        Returns
        -------
        d : `dict`
            Dictionary of extracted name-schema item sets.
 
        Raises
        ------
        ValueError
            Raised if the `sub` keyword argument is invalid without
            the `regex` argument.
 
            Also raised if an unknown keyword argument is supplied.
        """
        if kwargs.pop("ordered", False):
            d = collections.OrderedDict()
        else:
            d = dict()
        regex = kwargs.pop("regex", None)
        sub = kwargs.pop("sub", None)
        if sub is not None and regex is None:
            raise ValueError(
                "'sub' keyword argument to extract is invalid without 'regex' argument")
        if kwargs:
            kwargsStr = ", ".join(kwargs.keys())
            raise ValueError(f"Unrecognized keyword arguments for extract: {kwargsStr}")
        for item in self:
            trueName = item.field.getName()
            names = [trueName]
            for alias, target in self.getAliasMap().items():
                if trueName.startswith(target):
                    names.append(trueName.replace(target, alias, 1))
            for name in names:
                if regex is not None:
                    m = re.match(regex, name)
                    if m is not None:
                        if sub is not None:
                            name = m.expand(sub)
                        d[name] = item
                        continue  # continue middle loop so we don't match the same name twice
                for pattern in patterns:
                    if fnmatch.fnmatchcase(name, pattern):
                        d[name] = item
                        break  # break inner loop so we don't match the same name twice
        return d
 
    def __reduce__(self):
        """For pickle support."""
        fields = []
        for item in self:
            fields.append(item.field)
        return (makeSchemaFromFields, (fields,))
 
 
def makeSchemaFromFields(fields):
    """Create a Schema from a sequence of Fields. For pickle support.
 
    Parameters
    ----------
    fields : `tuple` ['lsst.afw.table.Field']
        The fields to construct the new Schema from.
 
    Returns
    -------
    schema : `lsst.afw.table.Schema`
        The constructed Schema.
    """
    schema = Schema()
    for field in fields:
        schema.addField(field)
    return schema