Coverage for python/lsst/pex/config/config.py: 61%
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1# This file is part of pex_config.
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 software is dual licensed under the GNU General Public License and also
10# under a 3-clause BSD license. Recipients may choose which of these licenses
11# to use; please see the files gpl-3.0.txt and/or bsd_license.txt,
12# respectively. If you choose the GPL option then the following text applies
13# (but note that there is still no warranty even if you opt for BSD instead):
14#
15# This program is free software: you can redistribute it and/or modify
16# it under the terms of the GNU General Public License as published by
17# the Free Software Foundation, either version 3 of the License, or
18# (at your option) any later version.
19#
20# This program is distributed in the hope that it will be useful,
21# but WITHOUT ANY WARRANTY; without even the implied warranty of
22# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23# GNU General Public License for more details.
24#
25# You should have received a copy of the GNU General Public License
26# along with this program. If not, see <http://www.gnu.org/licenses/>.
28__all__ = ("Config", "ConfigMeta", "Field", "FieldValidationError", "UnexpectedProxyUsageError")
30import copy
31import importlib
32import io
33import math
34import os
35import re
36import shutil
37import sys
38import tempfile
39import warnings
41# if YAML is not available that's fine and we simply don't register
42# the yaml representer since we know it won't be used.
43try:
44 import yaml
45except ImportError:
46 yaml = None
47 YamlLoaders = ()
48 doImport = None
50from .callStack import getCallStack, getStackFrame
51from .comparison import compareConfigs, compareScalars, getComparisonName
53if yaml: 53 ↛ 65line 53 didn't jump to line 65, because the condition on line 53 was never false
54 YamlLoaders = (yaml.Loader, yaml.FullLoader, yaml.SafeLoader, yaml.UnsafeLoader)
56 try:
57 # CLoader is not always available
58 from yaml import CLoader
60 YamlLoaders += (CLoader,)
61 except ImportError:
62 pass
65class UnexpectedProxyUsageError(TypeError):
66 """Exception raised when a proxy class is used in a context that suggests
67 it should have already been converted to the thing it proxies.
68 """
71def _joinNamePath(prefix=None, name=None, index=None):
72 """Generate nested configuration names."""
73 if not prefix and not name: 73 ↛ 74line 73 didn't jump to line 74, because the condition on line 73 was never true
74 raise ValueError("Invalid name: cannot be None")
75 elif not name: 75 ↛ 76line 75 didn't jump to line 76, because the condition on line 75 was never true
76 name = prefix
77 elif prefix and name: 77 ↛ 80line 77 didn't jump to line 80, because the condition on line 77 was never false
78 name = prefix + "." + name
80 if index is not None: 80 ↛ 81line 80 didn't jump to line 81, because the condition on line 80 was never true
81 return "%s[%r]" % (name, index)
82 else:
83 return name
86def _autocast(x, dtype):
87 """Cast a value to a type, if appropriate.
89 Parameters
90 ----------
91 x : object
92 A value.
93 dtype : tpye
94 Data type, such as `float`, `int`, or `str`.
96 Returns
97 -------
98 values : object
99 If appropriate, the returned value is ``x`` cast to the given type
100 ``dtype``. If the cast cannot be performed the original value of
101 ``x`` is returned.
102 """
103 if dtype == float and isinstance(x, int):
104 return float(x)
105 return x
108def _typeStr(x):
109 """Generate a fully-qualified type name.
111 Returns
112 -------
113 `str`
114 Fully-qualified type name.
116 Notes
117 -----
118 This function is used primarily for writing config files to be executed
119 later upon with the 'load' function.
120 """
121 if hasattr(x, "__module__") and hasattr(x, "__name__"):
122 xtype = x
123 else:
124 xtype = type(x)
125 if (sys.version_info.major <= 2 and xtype.__module__ == "__builtin__") or xtype.__module__ == "builtins": 125 ↛ 126line 125 didn't jump to line 126, because the condition on line 125 was never true
126 return xtype.__name__
127 else:
128 return "%s.%s" % (xtype.__module__, xtype.__name__)
131if yaml: 131 ↛ 164line 131 didn't jump to line 164, because the condition on line 131 was never false
133 def _yaml_config_representer(dumper, data):
134 """Represent a Config object in a form suitable for YAML.
136 Stores the serialized stream as a scalar block string.
137 """
138 stream = io.StringIO()
139 data.saveToStream(stream)
140 config_py = stream.getvalue()
142 # Strip multiple newlines from the end of the config
143 # This simplifies the YAML to use | and not |+
144 config_py = config_py.rstrip() + "\n"
146 # Trailing spaces force pyyaml to use non-block form.
147 # Remove the trailing spaces so it has no choice
148 config_py = re.sub(r"\s+$", "\n", config_py, flags=re.MULTILINE)
150 # Store the Python as a simple scalar
151 return dumper.represent_scalar("lsst.pex.config.Config", config_py, style="|")
153 def _yaml_config_constructor(loader, node):
154 """Construct a config from YAML"""
155 config_py = loader.construct_scalar(node)
156 return Config._fromPython(config_py)
158 # Register a generic constructor for Config and all subclasses
159 # Need to register for all the loaders we would like to use
160 for loader in YamlLoaders:
161 yaml.add_constructor("lsst.pex.config.Config", _yaml_config_constructor, Loader=loader)
164class ConfigMeta(type):
165 """A metaclass for `lsst.pex.config.Config`.
167 Notes
168 -----
169 ``ConfigMeta`` adds a dictionary containing all `~lsst.pex.config.Field`
170 class attributes as a class attribute called ``_fields``, and adds
171 the name of each field as an instance variable of the field itself (so you
172 don't have to pass the name of the field to the field constructor).
173 """
175 def __init__(cls, name, bases, dict_):
176 type.__init__(cls, name, bases, dict_)
177 cls._fields = {}
178 cls._source = getStackFrame()
180 def getFields(classtype):
181 fields = {}
182 bases = list(classtype.__bases__)
183 bases.reverse()
184 for b in bases:
185 fields.update(getFields(b))
187 for k, v in classtype.__dict__.items():
188 if isinstance(v, Field):
189 fields[k] = v
190 return fields
192 fields = getFields(cls)
193 for k, v in fields.items():
194 setattr(cls, k, copy.deepcopy(v))
196 def __setattr__(cls, name, value):
197 if isinstance(value, Field):
198 value.name = name
199 cls._fields[name] = value
200 type.__setattr__(cls, name, value)
203class FieldValidationError(ValueError):
204 """Raised when a ``~lsst.pex.config.Field`` is not valid in a
205 particular ``~lsst.pex.config.Config``.
207 Parameters
208 ----------
209 field : `lsst.pex.config.Field`
210 The field that was not valid.
211 config : `lsst.pex.config.Config`
212 The config containing the invalid field.
213 msg : `str`
214 Text describing why the field was not valid.
215 """
217 def __init__(self, field, config, msg):
218 self.fieldType = type(field)
219 """Type of the `~lsst.pex.config.Field` that incurred the error.
220 """
222 self.fieldName = field.name
223 """Name of the `~lsst.pex.config.Field` instance that incurred the
224 error (`str`).
226 See also
227 --------
228 lsst.pex.config.Field.name
229 """
231 self.fullname = _joinNamePath(config._name, field.name)
232 """Fully-qualified name of the `~lsst.pex.config.Field` instance
233 (`str`).
234 """
236 self.history = config.history.setdefault(field.name, [])
237 """Full history of all changes to the `~lsst.pex.config.Field`
238 instance.
239 """
241 self.fieldSource = field.source
242 """File and line number of the `~lsst.pex.config.Field` definition.
243 """
245 self.configSource = config._source
246 error = (
247 "%s '%s' failed validation: %s\n"
248 "For more information see the Field definition at:\n%s"
249 " and the Config definition at:\n%s"
250 % (
251 self.fieldType.__name__,
252 self.fullname,
253 msg,
254 self.fieldSource.format(),
255 self.configSource.format(),
256 )
257 )
258 super().__init__(error)
261class Field:
262 """A field in a `~lsst.pex.config.Config` that supports `int`, `float`,
263 `complex`, `bool`, and `str` data types.
265 Parameters
266 ----------
267 doc : `str`
268 A description of the field for users.
269 dtype : type
270 The field's data type. ``Field`` only supports basic data types:
271 `int`, `float`, `complex`, `bool`, and `str`. See
272 `Field.supportedTypes`.
273 default : object, optional
274 The field's default value.
275 check : callable, optional
276 A callable that is called with the field's value. This callable should
277 return `False` if the value is invalid. More complex inter-field
278 validation can be written as part of the
279 `lsst.pex.config.Config.validate` method.
280 optional : `bool`, optional
281 This sets whether the field is considered optional, and therefore
282 doesn't need to be set by the user. When `False`,
283 `lsst.pex.config.Config.validate` fails if the field's value is `None`.
284 deprecated : None or `str`, optional
285 A description of why this Field is deprecated, including removal date.
286 If not None, the string is appended to the docstring for this Field.
288 Raises
289 ------
290 ValueError
291 Raised when the ``dtype`` parameter is not one of the supported types
292 (see `Field.supportedTypes`).
294 See also
295 --------
296 ChoiceField
297 ConfigChoiceField
298 ConfigDictField
299 ConfigField
300 ConfigurableField
301 DictField
302 ListField
303 RangeField
304 RegistryField
306 Notes
307 -----
308 ``Field`` instances (including those of any subclass of ``Field``) are used
309 as class attributes of `~lsst.pex.config.Config` subclasses (see the
310 example, below). ``Field`` attributes work like the `property` attributes
311 of classes that implement custom setters and getters. `Field` attributes
312 belong to the class, but operate on the instance. Formally speaking,
313 `Field` attributes are `descriptors
314 <https://docs.python.org/3/howto/descriptor.html>`_.
316 When you access a `Field` attribute on a `Config` instance, you don't
317 get the `Field` instance itself. Instead, you get the value of that field,
318 which might be a simple type (`int`, `float`, `str`, `bool`) or a custom
319 container type (like a `lsst.pex.config.List`) depending on the field's
320 type. See the example, below.
322 Examples
323 --------
324 Instances of ``Field`` should be used as class attributes of
325 `lsst.pex.config.Config` subclasses:
327 >>> from lsst.pex.config import Config, Field
328 >>> class Example(Config):
329 ... myInt = Field("An integer field.", int, default=0)
330 ...
331 >>> print(config.myInt)
332 0
333 >>> config.myInt = 5
334 >>> print(config.myInt)
335 5
336 """
338 supportedTypes = set((str, bool, float, int, complex))
339 """Supported data types for field values (`set` of types).
340 """
342 def __init__(self, doc, dtype, default=None, check=None, optional=False, deprecated=None):
343 if dtype not in self.supportedTypes: 343 ↛ 344line 343 didn't jump to line 344, because the condition on line 343 was never true
344 raise ValueError("Unsupported Field dtype %s" % _typeStr(dtype))
346 source = getStackFrame()
347 self._setup(
348 doc=doc,
349 dtype=dtype,
350 default=default,
351 check=check,
352 optional=optional,
353 source=source,
354 deprecated=deprecated,
355 )
357 def _setup(self, doc, dtype, default, check, optional, source, deprecated):
358 """Set attributes, usually during initialization."""
359 self.dtype = dtype
360 """Data type for the field.
361 """
363 # append the deprecation message to the docstring.
364 if deprecated is not None:
365 doc = f"{doc} Deprecated: {deprecated}"
366 self.doc = doc
367 """A description of the field (`str`).
368 """
370 self.deprecated = deprecated
371 """If not None, a description of why this field is deprecated (`str`).
372 """
374 self.__doc__ = f"{doc} (`{dtype.__name__}`"
375 if optional or default is not None:
376 self.__doc__ += f", default ``{default!r}``"
377 self.__doc__ += ")"
379 self.default = default
380 """Default value for this field.
381 """
383 self.check = check
384 """A user-defined function that validates the value of the field.
385 """
387 self.optional = optional
388 """Flag that determines if the field is required to be set (`bool`).
390 When `False`, `lsst.pex.config.Config.validate` will fail if the
391 field's value is `None`.
392 """
394 self.source = source
395 """The stack frame where this field is defined (`list` of
396 `lsst.pex.config.callStack.StackFrame`).
397 """
399 def rename(self, instance):
400 """Rename the field in a `~lsst.pex.config.Config` (for internal use
401 only).
403 Parameters
404 ----------
405 instance : `lsst.pex.config.Config`
406 The config instance that contains this field.
408 Notes
409 -----
410 This method is invoked by the `lsst.pex.config.Config` object that
411 contains this field and should not be called directly.
413 Renaming is only relevant for `~lsst.pex.config.Field` instances that
414 hold subconfigs. `~lsst.pex.config.Fields` that hold subconfigs should
415 rename each subconfig with the full field name as generated by
416 `lsst.pex.config.config._joinNamePath`.
417 """
418 pass
420 def validate(self, instance):
421 """Validate the field (for internal use only).
423 Parameters
424 ----------
425 instance : `lsst.pex.config.Config`
426 The config instance that contains this field.
428 Raises
429 ------
430 lsst.pex.config.FieldValidationError
431 Raised if verification fails.
433 Notes
434 -----
435 This method provides basic validation:
437 - Ensures that the value is not `None` if the field is not optional.
438 - Ensures type correctness.
439 - Ensures that the user-provided ``check`` function is valid.
441 Most `~lsst.pex.config.Field` subclasses should call
442 `lsst.pex.config.field.Field.validate` if they re-implement
443 `~lsst.pex.config.field.Field.validate`.
444 """
445 value = self.__get__(instance)
446 if not self.optional and value is None:
447 raise FieldValidationError(self, instance, "Required value cannot be None")
449 def freeze(self, instance):
450 """Make this field read-only (for internal use only).
452 Parameters
453 ----------
454 instance : `lsst.pex.config.Config`
455 The config instance that contains this field.
457 Notes
458 -----
459 Freezing is only relevant for fields that hold subconfigs. Fields which
460 hold subconfigs should freeze each subconfig.
462 **Subclasses should implement this method.**
463 """
464 pass
466 def _validateValue(self, value):
467 """Validate a value.
469 Parameters
470 ----------
471 value : object
472 The value being validated.
474 Raises
475 ------
476 TypeError
477 Raised if the value's type is incompatible with the field's
478 ``dtype``.
479 ValueError
480 Raised if the value is rejected by the ``check`` method.
481 """
482 if value is None: 482 ↛ 483line 482 didn't jump to line 483, because the condition on line 482 was never true
483 return
485 if not isinstance(value, self.dtype): 485 ↛ 486line 485 didn't jump to line 486, because the condition on line 485 was never true
486 msg = "Value %s is of incorrect type %s. Expected type %s" % (
487 value,
488 _typeStr(value),
489 _typeStr(self.dtype),
490 )
491 raise TypeError(msg)
492 if self.check is not None and not self.check(value): 492 ↛ 493line 492 didn't jump to line 493, because the condition on line 492 was never true
493 msg = "Value %s is not a valid value" % str(value)
494 raise ValueError(msg)
496 def _collectImports(self, instance, imports):
497 """This function should call the _collectImports method on all config
498 objects the field may own, and union them with the supplied imports
499 set.
501 Parameters
502 ----------
503 instance : instance or subclass of `lsst.pex.config.Config`
504 A config object that has this field defined on it
505 imports : `set`
506 Set of python modules that need imported after persistence
507 """
508 pass
510 def save(self, outfile, instance):
511 """Save this field to a file (for internal use only).
513 Parameters
514 ----------
515 outfile : file-like object
516 A writeable field handle.
517 instance : `Config`
518 The `Config` instance that contains this field.
520 Notes
521 -----
522 This method is invoked by the `~lsst.pex.config.Config` object that
523 contains this field and should not be called directly.
525 The output consists of the documentation string
526 (`lsst.pex.config.Field.doc`) formatted as a Python comment. The second
527 line is formatted as an assignment: ``{fullname}={value}``.
529 This output can be executed with Python.
530 """
531 value = self.__get__(instance)
532 fullname = _joinNamePath(instance._name, self.name)
534 if self.deprecated and value == self.default: 534 ↛ 535line 534 didn't jump to line 535, because the condition on line 534 was never true
535 return
537 # write full documentation string as comment lines
538 # (i.e. first character is #)
539 doc = "# " + str(self.doc).replace("\n", "\n# ")
540 if isinstance(value, float) and not math.isfinite(value): 540 ↛ 542line 540 didn't jump to line 542, because the condition on line 540 was never true
541 # non-finite numbers need special care
542 outfile.write("{}\n{}=float('{!r}')\n\n".format(doc, fullname, value))
543 else:
544 outfile.write("{}\n{}={!r}\n\n".format(doc, fullname, value))
546 def toDict(self, instance):
547 """Convert the field value so that it can be set as the value of an
548 item in a `dict` (for internal use only).
550 Parameters
551 ----------
552 instance : `Config`
553 The `Config` that contains this field.
555 Returns
556 -------
557 value : object
558 The field's value. See *Notes*.
560 Notes
561 -----
562 This method invoked by the owning `~lsst.pex.config.Config` object and
563 should not be called directly.
565 Simple values are passed through. Complex data structures must be
566 manipulated. For example, a `~lsst.pex.config.Field` holding a
567 subconfig should, instead of the subconfig object, return a `dict`
568 where the keys are the field names in the subconfig, and the values are
569 the field values in the subconfig.
570 """
571 return self.__get__(instance)
573 def __get__(self, instance, owner=None, at=None, label="default"):
574 """Define how attribute access should occur on the Config instance
575 This is invoked by the owning config object and should not be called
576 directly
578 When the field attribute is accessed on a Config class object, it
579 returns the field object itself in order to allow inspection of
580 Config classes.
582 When the field attribute is access on a config instance, the actual
583 value described by the field (and held by the Config instance) is
584 returned.
585 """
586 if instance is None: 586 ↛ 587line 586 didn't jump to line 587, because the condition on line 586 was never true
587 return self
588 else:
589 # try statements are almost free in python if they succeed
590 try:
591 return instance._storage[self.name]
592 except AttributeError:
593 if not isinstance(instance, Config):
594 return self
595 else:
596 raise AttributeError(
597 f"Config {instance} is missing "
598 "_storage attribute, likely"
599 " incorrectly initialized"
600 )
602 def __set__(self, instance, value, at=None, label="assignment"):
603 """Set an attribute on the config instance.
605 Parameters
606 ----------
607 instance : `lsst.pex.config.Config`
608 The config instance that contains this field.
609 value : obj
610 Value to set on this field.
611 at : `list` of `lsst.pex.config.callStack.StackFrame`
612 The call stack (created by
613 `lsst.pex.config.callStack.getCallStack`).
614 label : `str`, optional
615 Event label for the history.
617 Notes
618 -----
619 This method is invoked by the owning `lsst.pex.config.Config` object
620 and should not be called directly.
622 Derived `~lsst.pex.config.Field` classes may need to override the
623 behavior. When overriding ``__set__``, `~lsst.pex.config.Field` authors
624 should follow the following rules:
626 - Do not allow modification of frozen configs.
627 - Validate the new value **before** modifying the field. Except if the
628 new value is `None`. `None` is special and no attempt should be made
629 to validate it until `lsst.pex.config.Config.validate` is called.
630 - Do not modify the `~lsst.pex.config.Config` instance to contain
631 invalid values.
632 - If the field is modified, update the history of the
633 `lsst.pex.config.field.Field` to reflect the changes.
635 In order to decrease the need to implement this method in derived
636 `~lsst.pex.config.Field` types, value validation is performed in the
637 `lsst.pex.config.Field._validateValue`. If only the validation step
638 differs in the derived `~lsst.pex.config.Field`, it is simpler to
639 implement `lsst.pex.config.Field._validateValue` than to reimplement
640 ``__set__``. More complicated behavior, however, may require
641 reimplementation.
642 """
643 if instance._frozen: 643 ↛ 644line 643 didn't jump to line 644, because the condition on line 643 was never true
644 raise FieldValidationError(self, instance, "Cannot modify a frozen Config")
646 history = instance._history.setdefault(self.name, [])
647 if value is not None: 647 ↛ 654line 647 didn't jump to line 654, because the condition on line 647 was never false
648 value = _autocast(value, self.dtype)
649 try:
650 self._validateValue(value)
651 except BaseException as e:
652 raise FieldValidationError(self, instance, str(e))
654 instance._storage[self.name] = value
655 if at is None: 655 ↛ 656line 655 didn't jump to line 656, because the condition on line 655 was never true
656 at = getCallStack()
657 history.append((value, at, label))
659 def __delete__(self, instance, at=None, label="deletion"):
660 """Delete an attribute from a `lsst.pex.config.Config` instance.
662 Parameters
663 ----------
664 instance : `lsst.pex.config.Config`
665 The config instance that contains this field.
666 at : `list` of `lsst.pex.config.callStack.StackFrame`
667 The call stack (created by
668 `lsst.pex.config.callStack.getCallStack`).
669 label : `str`, optional
670 Event label for the history.
672 Notes
673 -----
674 This is invoked by the owning `~lsst.pex.config.Config` object and
675 should not be called directly.
676 """
677 if at is None:
678 at = getCallStack()
679 self.__set__(instance, None, at=at, label=label)
681 def _compare(self, instance1, instance2, shortcut, rtol, atol, output):
682 """Compare a field (named `Field.name`) in two
683 `~lsst.pex.config.Config` instances for equality.
685 Parameters
686 ----------
687 instance1 : `lsst.pex.config.Config`
688 Left-hand side `Config` instance to compare.
689 instance2 : `lsst.pex.config.Config`
690 Right-hand side `Config` instance to compare.
691 shortcut : `bool`, optional
692 **Unused.**
693 rtol : `float`, optional
694 Relative tolerance for floating point comparisons.
695 atol : `float`, optional
696 Absolute tolerance for floating point comparisons.
697 output : callable, optional
698 A callable that takes a string, used (possibly repeatedly) to
699 report inequalities.
701 Notes
702 -----
703 This method must be overridden by more complex `Field` subclasses.
705 See also
706 --------
707 lsst.pex.config.compareScalars
708 """
709 v1 = getattr(instance1, self.name)
710 v2 = getattr(instance2, self.name)
711 name = getComparisonName(
712 _joinNamePath(instance1._name, self.name), _joinNamePath(instance2._name, self.name)
713 )
714 return compareScalars(name, v1, v2, dtype=self.dtype, rtol=rtol, atol=atol, output=output)
717class RecordingImporter:
718 """Importer (for `sys.meta_path`) that records which modules are being
719 imported.
721 *This class does not do any importing itself.*
723 Examples
724 --------
725 Use this class as a context manager to ensure it is properly uninstalled
726 when done:
728 >>> with RecordingImporter() as importer:
729 ... # import stuff
730 ... import numpy as np
731 ... print("Imported: " + importer.getModules())
732 """
734 def __init__(self):
735 self._modules = set()
737 def __enter__(self):
738 self.origMetaPath = sys.meta_path
739 sys.meta_path = [self] + sys.meta_path
740 return self
742 def __exit__(self, *args):
743 self.uninstall()
744 return False # Don't suppress exceptions
746 def uninstall(self):
747 """Uninstall the importer."""
748 sys.meta_path = self.origMetaPath
750 def find_module(self, fullname, path=None):
751 """Called as part of the ``import`` chain of events."""
752 self._modules.add(fullname)
753 # Return None because we don't do any importing.
754 return None
756 def getModules(self):
757 """Get the set of modules that were imported.
759 Returns
760 -------
761 modules : `set` of `str`
762 Set of imported module names.
763 """
764 return self._modules
767class Config(metaclass=ConfigMeta):
768 """Base class for configuration (*config*) objects.
770 Notes
771 -----
772 A ``Config`` object will usually have several `~lsst.pex.config.Field`
773 instances as class attributes. These are used to define most of the base
774 class behavior.
776 ``Config`` implements a mapping API that provides many `dict`-like methods,
777 such as `keys`, `values`, `items`, `iteritems`, `iterkeys`, and
778 `itervalues`. ``Config`` instances also support the ``in`` operator to
779 test if a field is in the config. Unlike a `dict`, ``Config`` classes are
780 not subscriptable. Instead, access individual fields as attributes of the
781 configuration instance.
783 Examples
784 --------
785 Config classes are subclasses of ``Config`` that have
786 `~lsst.pex.config.Field` instances (or instances of
787 `~lsst.pex.config.Field` subclasses) as class attributes:
789 >>> from lsst.pex.config import Config, Field, ListField
790 >>> class DemoConfig(Config):
791 ... intField = Field(doc="An integer field", dtype=int, default=42)
792 ... listField = ListField(doc="List of favorite beverages.", dtype=str,
793 ... default=['coffee', 'green tea', 'water'])
794 ...
795 >>> config = DemoConfig()
797 Configs support many `dict`-like APIs:
799 >>> config.keys()
800 ['intField', 'listField']
801 >>> 'intField' in config
802 True
804 Individual fields can be accessed as attributes of the configuration:
806 >>> config.intField
807 42
808 >>> config.listField.append('earl grey tea')
809 >>> print(config.listField)
810 ['coffee', 'green tea', 'water', 'earl grey tea']
811 """
813 def __iter__(self):
814 """Iterate over fields."""
815 return self._fields.__iter__()
817 def keys(self):
818 """Get field names.
820 Returns
821 -------
822 names : `list`
823 List of `lsst.pex.config.Field` names.
825 See also
826 --------
827 lsst.pex.config.Config.iterkeys
828 """
829 return list(self._storage.keys())
831 def values(self):
832 """Get field values.
834 Returns
835 -------
836 values : `list`
837 List of field values.
839 See also
840 --------
841 lsst.pex.config.Config.itervalues
842 """
843 return list(self._storage.values())
845 def items(self):
846 """Get configurations as ``(field name, field value)`` pairs.
848 Returns
849 -------
850 items : `list`
851 List of tuples for each configuration. Tuple items are:
853 0. Field name.
854 1. Field value.
856 See also
857 --------
858 lsst.pex.config.Config.iteritems
859 """
860 return list(self._storage.items())
862 def iteritems(self):
863 """Iterate over (field name, field value) pairs.
865 Yields
866 ------
867 item : `tuple`
868 Tuple items are:
870 0. Field name.
871 1. Field value.
873 See also
874 --------
875 lsst.pex.config.Config.items
876 """
877 return iter(self._storage.items())
879 def itervalues(self):
880 """Iterate over field values.
882 Yields
883 ------
884 value : obj
885 A field value.
887 See also
888 --------
889 lsst.pex.config.Config.values
890 """
891 return iter(self.storage.values())
893 def iterkeys(self):
894 """Iterate over field names
896 Yields
897 ------
898 key : `str`
899 A field's key (attribute name).
901 See also
902 --------
903 lsst.pex.config.Config.values
904 """
905 return iter(self.storage.keys())
907 def __contains__(self, name):
908 """!Return True if the specified field exists in this config
910 @param[in] name field name to test for
911 """
912 return self._storage.__contains__(name)
914 def __new__(cls, *args, **kw):
915 """Allocate a new `lsst.pex.config.Config` object.
917 In order to ensure that all Config object are always in a proper state
918 when handed to users or to derived `~lsst.pex.config.Config` classes,
919 some attributes are handled at allocation time rather than at
920 initialization.
922 This ensures that even if a derived `~lsst.pex.config.Config` class
923 implements ``__init__``, its author does not need to be concerned about
924 when or even the base ``Config.__init__`` should be called.
925 """
926 name = kw.pop("__name", None)
927 at = kw.pop("__at", getCallStack())
928 # remove __label and ignore it
929 kw.pop("__label", "default")
931 instance = object.__new__(cls)
932 instance._frozen = False
933 instance._name = name
934 instance._storage = {}
935 instance._history = {}
936 instance._imports = set()
937 # load up defaults
938 for field in instance._fields.values():
939 instance._history[field.name] = []
940 field.__set__(instance, field.default, at=at + [field.source], label="default")
941 # set custom default-overides
942 instance.setDefaults()
943 # set constructor overides
944 instance.update(__at=at, **kw)
945 return instance
947 def __reduce__(self):
948 """Reduction for pickling (function with arguments to reproduce).
950 We need to condense and reconstitute the `~lsst.pex.config.Config`,
951 since it may contain lambdas (as the ``check`` elements) that cannot
952 be pickled.
953 """
954 # The stream must be in characters to match the API but pickle
955 # requires bytes
956 stream = io.StringIO()
957 self.saveToStream(stream)
958 return (unreduceConfig, (self.__class__, stream.getvalue().encode()))
960 def setDefaults(self):
961 """Subclass hook for computing defaults.
963 Notes
964 -----
965 Derived `~lsst.pex.config.Config` classes that must compute defaults
966 rather than using the `~lsst.pex.config.Field` instances's defaults
967 should do so here. To correctly use inherited defaults,
968 implementations of ``setDefaults`` must call their base class's
969 ``setDefaults``.
970 """
971 pass
973 def update(self, **kw):
974 """Update values of fields specified by the keyword arguments.
976 Parameters
977 ----------
978 kw
979 Keywords are configuration field names. Values are configuration
980 field values.
982 Notes
983 -----
984 The ``__at`` and ``__label`` keyword arguments are special internal
985 keywords. They are used to strip out any internal steps from the
986 history tracebacks of the config. Do not modify these keywords to
987 subvert a `~lsst.pex.config.Config` instance's history.
989 Examples
990 --------
991 This is a config with three fields:
993 >>> from lsst.pex.config import Config, Field
994 >>> class DemoConfig(Config):
995 ... fieldA = Field(doc='Field A', dtype=int, default=42)
996 ... fieldB = Field(doc='Field B', dtype=bool, default=True)
997 ... fieldC = Field(doc='Field C', dtype=str, default='Hello world')
998 ...
999 >>> config = DemoConfig()
1001 These are the default values of each field:
1003 >>> for name, value in config.iteritems():
1004 ... print(f"{name}: {value}")
1005 ...
1006 fieldA: 42
1007 fieldB: True
1008 fieldC: 'Hello world'
1010 Using this method to update ``fieldA`` and ``fieldC``:
1012 >>> config.update(fieldA=13, fieldC='Updated!')
1014 Now the values of each field are:
1016 >>> for name, value in config.iteritems():
1017 ... print(f"{name}: {value}")
1018 ...
1019 fieldA: 13
1020 fieldB: True
1021 fieldC: 'Updated!'
1022 """
1023 at = kw.pop("__at", getCallStack())
1024 label = kw.pop("__label", "update")
1026 for name, value in kw.items():
1027 try:
1028 field = self._fields[name]
1029 field.__set__(self, value, at=at, label=label)
1030 except KeyError:
1031 raise KeyError("No field of name %s exists in config type %s" % (name, _typeStr(self)))
1033 def load(self, filename, root="config"):
1034 """Modify this config in place by executing the Python code in a
1035 configuration file.
1037 Parameters
1038 ----------
1039 filename : `str`
1040 Name of the configuration file. A configuration file is Python
1041 module.
1042 root : `str`, optional
1043 Name of the variable in file that refers to the config being
1044 overridden.
1046 For example, the value of root is ``"config"`` and the file
1047 contains::
1049 config.myField = 5
1051 Then this config's field ``myField`` is set to ``5``.
1053 **Deprecated:** For backwards compatibility, older config files
1054 that use ``root="root"`` instead of ``root="config"`` will be
1055 loaded with a warning printed to `sys.stderr`. This feature will be
1056 removed at some point.
1058 See also
1059 --------
1060 lsst.pex.config.Config.loadFromStream
1061 lsst.pex.config.Config.loadFromString
1062 lsst.pex.config.Config.save
1063 lsst.pex.config.Config.saveToStream
1064 lsst.pex.config.Config.saveToString
1065 """
1066 with open(filename, "r") as f:
1067 code = compile(f.read(), filename=filename, mode="exec")
1068 self.loadFromString(code, root=root, filename=filename)
1070 def loadFromStream(self, stream, root="config", filename=None):
1071 """Modify this Config in place by executing the Python code in the
1072 provided stream.
1074 Parameters
1075 ----------
1076 stream : file-like object, `str`, `bytes`, or compiled string
1077 Stream containing configuration override code. If this is a
1078 code object, it should be compiled with ``mode="exec"``.
1079 root : `str`, optional
1080 Name of the variable in file that refers to the config being
1081 overridden.
1083 For example, the value of root is ``"config"`` and the file
1084 contains::
1086 config.myField = 5
1088 Then this config's field ``myField`` is set to ``5``.
1090 **Deprecated:** For backwards compatibility, older config files
1091 that use ``root="root"`` instead of ``root="config"`` will be
1092 loaded with a warning printed to `sys.stderr`. This feature will be
1093 removed at some point.
1094 filename : `str`, optional
1095 Name of the configuration file, or `None` if unknown or contained
1096 in the stream. Used for error reporting.
1098 Notes
1099 -----
1100 For backwards compatibility reasons, this method accepts strings, bytes
1101 and code objects as well as file-like objects. New code should use
1102 `loadFromString` instead for most of these types.
1104 See also
1105 --------
1106 lsst.pex.config.Config.load
1107 lsst.pex.config.Config.loadFromString
1108 lsst.pex.config.Config.save
1109 lsst.pex.config.Config.saveToStream
1110 lsst.pex.config.Config.saveToString
1111 """
1112 if hasattr(stream, "read"): 1112 ↛ 1113line 1112 didn't jump to line 1113, because the condition on line 1112 was never true
1113 if filename is None:
1114 filename = getattr(stream, "name", "?")
1115 code = compile(stream.read(), filename=filename, mode="exec")
1116 else:
1117 code = stream
1118 self.loadFromString(code, root=root, filename=filename)
1120 def loadFromString(self, code, root="config", filename=None):
1121 """Modify this Config in place by executing the Python code in the
1122 provided string.
1124 Parameters
1125 ----------
1126 code : `str`, `bytes`, or compiled string
1127 Stream containing configuration override code.
1128 root : `str`, optional
1129 Name of the variable in file that refers to the config being
1130 overridden.
1132 For example, the value of root is ``"config"`` and the file
1133 contains::
1135 config.myField = 5
1137 Then this config's field ``myField`` is set to ``5``.
1139 **Deprecated:** For backwards compatibility, older config files
1140 that use ``root="root"`` instead of ``root="config"`` will be
1141 loaded with a warning printed to `sys.stderr`. This feature will be
1142 removed at some point.
1143 filename : `str`, optional
1144 Name of the configuration file, or `None` if unknown or contained
1145 in the stream. Used for error reporting.
1147 See also
1148 --------
1149 lsst.pex.config.Config.load
1150 lsst.pex.config.Config.loadFromStream
1151 lsst.pex.config.Config.save
1152 lsst.pex.config.Config.saveToStream
1153 lsst.pex.config.Config.saveToString
1154 """
1155 if filename is None: 1155 ↛ 1159line 1155 didn't jump to line 1159, because the condition on line 1155 was never false
1156 # try to determine the file name; a compiled string
1157 # has attribute "co_filename",
1158 filename = getattr(code, "co_filename", "?")
1159 with RecordingImporter() as importer:
1160 globals = {"__file__": filename}
1161 try:
1162 local = {root: self}
1163 exec(code, globals, local)
1164 except NameError as e:
1165 if root == "config" and "root" in e.args[0]:
1166 print(
1167 f"Config override file {filename!r}"
1168 " appears to use 'root' instead of 'config'; trying with 'root'",
1169 file=sys.stderr,
1170 )
1171 local = {"root": self}
1172 exec(code, globals, local)
1173 else:
1174 raise
1176 self._imports.update(importer.getModules())
1178 def save(self, filename, root="config"):
1179 """Save a Python script to the named file, which, when loaded,
1180 reproduces this config.
1182 Parameters
1183 ----------
1184 filename : `str`
1185 Desination filename of this configuration.
1186 root : `str`, optional
1187 Name to use for the root config variable. The same value must be
1188 used when loading (see `lsst.pex.config.Config.load`).
1190 See also
1191 --------
1192 lsst.pex.config.Config.saveToStream
1193 lsst.pex.config.Config.saveToString
1194 lsst.pex.config.Config.load
1195 lsst.pex.config.Config.loadFromStream
1196 lsst.pex.config.Config.loadFromString
1197 """
1198 d = os.path.dirname(filename)
1199 with tempfile.NamedTemporaryFile(mode="w", delete=False, dir=d) as outfile:
1200 self.saveToStream(outfile, root)
1201 # tempfile is hardcoded to create files with mode '0600'
1202 # for an explantion of these antics see:
1203 # https://stackoverflow.com/questions/10291131/how-to-use-os-umask-in-python
1204 umask = os.umask(0o077)
1205 os.umask(umask)
1206 os.chmod(outfile.name, (~umask & 0o666))
1207 # chmod before the move so we get quasi-atomic behavior if the
1208 # source and dest. are on the same filesystem.
1209 # os.rename may not work across filesystems
1210 shutil.move(outfile.name, filename)
1212 def saveToString(self, skipImports=False):
1213 """Return the Python script form of this configuration as an executable
1214 string.
1216 Parameters
1217 ----------
1218 skipImports : `bool`, optional
1219 If `True` then do not include ``import`` statements in output,
1220 this is to support human-oriented output from ``pipetask`` where
1221 additional clutter is not useful.
1223 Returns
1224 -------
1225 code : `str`
1226 A code string readable by `loadFromString`.
1228 See also
1229 --------
1230 lsst.pex.config.Config.save
1231 lsst.pex.config.Config.saveToStream
1232 lsst.pex.config.Config.load
1233 lsst.pex.config.Config.loadFromStream
1234 lsst.pex.config.Config.loadFromString
1235 """
1236 buffer = io.StringIO()
1237 self.saveToStream(buffer, skipImports=skipImports)
1238 return buffer.getvalue()
1240 def saveToStream(self, outfile, root="config", skipImports=False):
1241 """Save a configuration file to a stream, which, when loaded,
1242 reproduces this config.
1244 Parameters
1245 ----------
1246 outfile : file-like object
1247 Destination file object write the config into. Accepts strings not
1248 bytes.
1249 root
1250 Name to use for the root config variable. The same value must be
1251 used when loading (see `lsst.pex.config.Config.load`).
1252 skipImports : `bool`, optional
1253 If `True` then do not include ``import`` statements in output,
1254 this is to support human-oriented output from ``pipetask`` where
1255 additional clutter is not useful.
1257 See also
1258 --------
1259 lsst.pex.config.Config.save
1260 lsst.pex.config.Config.saveToString
1261 lsst.pex.config.Config.load
1262 lsst.pex.config.Config.loadFromStream
1263 lsst.pex.config.Config.loadFromString
1264 """
1265 tmp = self._name
1266 self._rename(root)
1267 try:
1268 if not skipImports: 1268 ↛ 1282line 1268 didn't jump to line 1282, because the condition on line 1268 was never false
1269 self._collectImports()
1270 # Remove self from the set, as it is handled explicitly below
1271 self._imports.remove(self.__module__)
1272 configType = type(self)
1273 typeString = _typeStr(configType)
1274 outfile.write(f"import {configType.__module__}\n")
1275 outfile.write(
1276 f"assert type({root})=={typeString}, 'config is of type %s.%s instead of "
1277 f"{typeString}' % (type({root}).__module__, type({root}).__name__)\n"
1278 )
1279 for imp in self._imports: 1279 ↛ 1280line 1279 didn't jump to line 1280, because the loop on line 1279 never started
1280 if imp in sys.modules and sys.modules[imp] is not None:
1281 outfile.write("import {}\n".format(imp))
1282 self._save(outfile)
1283 finally:
1284 self._rename(tmp)
1286 def freeze(self):
1287 """Make this config, and all subconfigs, read-only."""
1288 self._frozen = True
1289 for field in self._fields.values():
1290 field.freeze(self)
1292 def _save(self, outfile):
1293 """Save this config to an open stream object.
1295 Parameters
1296 ----------
1297 outfile : file-like object
1298 Destination file object write the config into. Accepts strings not
1299 bytes.
1300 """
1301 for field in self._fields.values():
1302 field.save(outfile, self)
1304 def _collectImports(self):
1305 """Adds module containing self to the list of things to import and
1306 then loops over all the fields in the config calling a corresponding
1307 collect method. The field method will call _collectImports on any
1308 configs it may own and return the set of things to import. This
1309 returned set will be merged with the set of imports for this config
1310 class.
1311 """
1312 self._imports.add(self.__module__)
1313 for name, field in self._fields.items():
1314 field._collectImports(self, self._imports)
1316 def toDict(self):
1317 """Make a dictionary of field names and their values.
1319 Returns
1320 -------
1321 dict_ : `dict`
1322 Dictionary with keys that are `~lsst.pex.config.Field` names.
1323 Values are `~lsst.pex.config.Field` values.
1325 See also
1326 --------
1327 lsst.pex.config.Field.toDict
1329 Notes
1330 -----
1331 This method uses the `~lsst.pex.config.Field.toDict` method of
1332 individual fields. Subclasses of `~lsst.pex.config.Field` may need to
1333 implement a ``toDict`` method for *this* method to work.
1334 """
1335 dict_ = {}
1336 for name, field in self._fields.items():
1337 dict_[name] = field.toDict(self)
1338 return dict_
1340 def names(self):
1341 """Get all the field names in the config, recursively.
1343 Returns
1344 -------
1345 names : `list` of `str`
1346 Field names.
1347 """
1348 #
1349 # Rather than sort out the recursion all over again use the
1350 # pre-existing saveToStream()
1351 #
1352 with io.StringIO() as strFd:
1353 self.saveToStream(strFd, "config")
1354 contents = strFd.getvalue()
1355 strFd.close()
1356 #
1357 # Pull the names out of the dumped config
1358 #
1359 keys = []
1360 for line in contents.split("\n"):
1361 if re.search(r"^((assert|import)\s+|\s*$|#)", line):
1362 continue
1364 mat = re.search(r"^(?:config\.)?([^=]+)\s*=\s*.*", line)
1365 if mat:
1366 keys.append(mat.group(1))
1368 return keys
1370 def _rename(self, name):
1371 """Rename this config object in its parent `~lsst.pex.config.Config`.
1373 Parameters
1374 ----------
1375 name : `str`
1376 New name for this config in its parent `~lsst.pex.config.Config`.
1378 Notes
1379 -----
1380 This method uses the `~lsst.pex.config.Field.rename` method of
1381 individual `lsst.pex.config.Field` instances.
1382 `lsst.pex.config.Field` subclasses may need to implement a ``rename``
1383 method for *this* method to work.
1385 See also
1386 --------
1387 lsst.pex.config.Field.rename
1388 """
1389 self._name = name
1390 for field in self._fields.values():
1391 field.rename(self)
1393 def validate(self):
1394 """Validate the Config, raising an exception if invalid.
1396 Raises
1397 ------
1398 lsst.pex.config.FieldValidationError
1399 Raised if verification fails.
1401 Notes
1402 -----
1403 The base class implementation performs type checks on all fields by
1404 calling their `~lsst.pex.config.Field.validate` methods.
1406 Complex single-field validation can be defined by deriving new Field
1407 types. For convenience, some derived `lsst.pex.config.Field`-types
1408 (`~lsst.pex.config.ConfigField` and
1409 `~lsst.pex.config.ConfigChoiceField`) are defined in `lsst.pex.config`
1410 that handle recursing into subconfigs.
1412 Inter-field relationships should only be checked in derived
1413 `~lsst.pex.config.Config` classes after calling this method, and base
1414 validation is complete.
1415 """
1416 for field in self._fields.values():
1417 field.validate(self)
1419 def formatHistory(self, name, **kwargs):
1420 """Format a configuration field's history to a human-readable format.
1422 Parameters
1423 ----------
1424 name : `str`
1425 Name of a `~lsst.pex.config.Field` in this config.
1426 kwargs
1427 Keyword arguments passed to `lsst.pex.config.history.format`.
1429 Returns
1430 -------
1431 history : `str`
1432 A string containing the formatted history.
1434 See also
1435 --------
1436 lsst.pex.config.history.format
1437 """
1438 import lsst.pex.config.history as pexHist
1440 return pexHist.format(self, name, **kwargs)
1442 history = property(lambda x: x._history) 1442 ↛ exitline 1442 didn't run the lambda on line 1442
1443 """Read-only history.
1444 """
1446 def __setattr__(self, attr, value, at=None, label="assignment"):
1447 """Set an attribute (such as a field's value).
1449 Notes
1450 -----
1451 Unlike normal Python objects, `~lsst.pex.config.Config` objects are
1452 locked such that no additional attributes nor properties may be added
1453 to them dynamically.
1455 Although this is not the standard Python behavior, it helps to protect
1456 users from accidentally mispelling a field name, or trying to set a
1457 non-existent field.
1458 """
1459 if attr in self._fields:
1460 if self._fields[attr].deprecated is not None: 1460 ↛ 1461line 1460 didn't jump to line 1461, because the condition on line 1460 was never true
1461 fullname = _joinNamePath(self._name, self._fields[attr].name)
1462 warnings.warn(
1463 f"Config field {fullname} is deprecated: {self._fields[attr].deprecated}",
1464 FutureWarning,
1465 stacklevel=2,
1466 )
1467 if at is None: 1467 ↛ 1470line 1467 didn't jump to line 1470, because the condition on line 1467 was never false
1468 at = getCallStack()
1469 # This allows Field descriptors to work.
1470 self._fields[attr].__set__(self, value, at=at, label=label)
1471 elif hasattr(getattr(self.__class__, attr, None), "__set__"): 1471 ↛ 1473line 1471 didn't jump to line 1473, because the condition on line 1471 was never true
1472 # This allows properties and other non-Field descriptors to work.
1473 return object.__setattr__(self, attr, value)
1474 elif attr in self.__dict__ or attr in ("_name", "_history", "_storage", "_frozen", "_imports"): 1474 ↛ 1479line 1474 didn't jump to line 1479, because the condition on line 1474 was never false
1475 # This allows specific private attributes to work.
1476 self.__dict__[attr] = value
1477 else:
1478 # We throw everything else.
1479 raise AttributeError("%s has no attribute %s" % (_typeStr(self), attr))
1481 def __delattr__(self, attr, at=None, label="deletion"):
1482 if attr in self._fields:
1483 if at is None:
1484 at = getCallStack()
1485 self._fields[attr].__delete__(self, at=at, label=label)
1486 else:
1487 object.__delattr__(self, attr)
1489 def __eq__(self, other):
1490 if type(other) == type(self): 1490 ↛ 1491line 1490 didn't jump to line 1491, because the condition on line 1490 was never true
1491 for name in self._fields:
1492 thisValue = getattr(self, name)
1493 otherValue = getattr(other, name)
1494 if isinstance(thisValue, float) and math.isnan(thisValue):
1495 if not math.isnan(otherValue):
1496 return False
1497 elif thisValue != otherValue:
1498 return False
1499 return True
1500 return False
1502 def __ne__(self, other):
1503 return not self.__eq__(other)
1505 def __str__(self):
1506 return str(self.toDict())
1508 def __repr__(self):
1509 return "%s(%s)" % (
1510 _typeStr(self),
1511 ", ".join("%s=%r" % (k, v) for k, v in self.toDict().items() if v is not None),
1512 )
1514 def compare(self, other, shortcut=True, rtol=1e-8, atol=1e-8, output=None):
1515 """Compare this configuration to another `~lsst.pex.config.Config` for
1516 equality.
1518 Parameters
1519 ----------
1520 other : `lsst.pex.config.Config`
1521 Other `~lsst.pex.config.Config` object to compare against this
1522 config.
1523 shortcut : `bool`, optional
1524 If `True`, return as soon as an inequality is found. Default is
1525 `True`.
1526 rtol : `float`, optional
1527 Relative tolerance for floating point comparisons.
1528 atol : `float`, optional
1529 Absolute tolerance for floating point comparisons.
1530 output : callable, optional
1531 A callable that takes a string, used (possibly repeatedly) to
1532 report inequalities.
1534 Returns
1535 -------
1536 isEqual : `bool`
1537 `True` when the two `lsst.pex.config.Config` instances are equal.
1538 `False` if there is an inequality.
1540 See also
1541 --------
1542 lsst.pex.config.compareConfigs
1544 Notes
1545 -----
1546 Unselected targets of `~lsst.pex.config.RegistryField` fields and
1547 unselected choices of `~lsst.pex.config.ConfigChoiceField` fields
1548 are not considered by this method.
1550 Floating point comparisons are performed by `numpy.allclose`.
1551 """
1552 name1 = self._name if self._name is not None else "config"
1553 name2 = other._name if other._name is not None else "config"
1554 name = getComparisonName(name1, name2)
1555 return compareConfigs(name, self, other, shortcut=shortcut, rtol=rtol, atol=atol, output=output)
1557 @classmethod
1558 def __init_subclass__(cls, **kwargs):
1559 """Run initialization for every subclass.
1561 Specifically registers the subclass with a YAML representer
1562 and YAML constructor (if pyyaml is available)
1563 """
1564 super().__init_subclass__(**kwargs)
1566 if not yaml: 1566 ↛ 1567line 1566 didn't jump to line 1567, because the condition on line 1566 was never true
1567 return
1569 yaml.add_representer(cls, _yaml_config_representer)
1571 @classmethod
1572 def _fromPython(cls, config_py):
1573 """Instantiate a `Config`-subclass from serialized Python form.
1575 Parameters
1576 ----------
1577 config_py : `str`
1578 A serialized form of the Config as created by
1579 `Config.saveToStream`.
1581 Returns
1582 -------
1583 config : `Config`
1584 Reconstructed `Config` instant.
1585 """
1586 cls = _classFromPython(config_py)
1587 return unreduceConfig(cls, config_py)
1590def _classFromPython(config_py):
1591 """Return the Config subclass required by this Config serialization.
1593 Parameters
1594 ----------
1595 config_py : `str`
1596 A serialized form of the Config as created by
1597 `Config.saveToStream`.
1599 Returns
1600 -------
1601 cls : `type`
1602 The `Config` subclass associated with this config.
1603 """
1604 # standard serialization has the form:
1605 # import config.class
1606 # assert type(config)==config.class.Config, ...
1607 # We want to parse these two lines so we can get the class itself
1609 # Do a single regex to avoid large string copies when splitting a
1610 # large config into separate lines.
1611 matches = re.search(r"^import ([\w.]+)\nassert .*==(.*?),", config_py)
1613 if not matches:
1614 first_line, second_line, _ = config_py.split("\n", 2)
1615 raise ValueError(
1616 "First two lines did not match expected form. Got:\n" f" - {first_line}\n" f" - {second_line}"
1617 )
1619 module_name = matches.group(1)
1620 module = importlib.import_module(module_name)
1622 # Second line
1623 full_name = matches.group(2)
1625 # Remove the module name from the full name
1626 if not full_name.startswith(module_name):
1627 raise ValueError(f"Module name ({module_name}) inconsistent with full name ({full_name})")
1629 # if module name is a.b.c and full name is a.b.c.d.E then
1630 # we need to remove a.b.c. and iterate over the remainder
1631 # The +1 is for the extra dot after a.b.c
1632 remainder = full_name[len(module_name) + 1 :]
1633 components = remainder.split(".")
1634 pytype = module
1635 for component in components:
1636 pytype = getattr(pytype, component)
1637 return pytype
1640def unreduceConfig(cls, stream):
1641 """Create a `~lsst.pex.config.Config` from a stream.
1643 Parameters
1644 ----------
1645 cls : `lsst.pex.config.Config`-type
1646 A `lsst.pex.config.Config` type (not an instance) that is instantiated
1647 with configurations in the ``stream``.
1648 stream : file-like object, `str`, or compiled string
1649 Stream containing configuration override code.
1651 Returns
1652 -------
1653 config : `lsst.pex.config.Config`
1654 Config instance.
1656 See also
1657 --------
1658 lsst.pex.config.Config.loadFromStream
1659 """
1660 config = cls()
1661 config.loadFromStream(stream)
1662 return config