structured_data.match.ProcessorList.__init__() - Code Metrics - Inspection of "Factor out common MatchDict logic" - mwchase/python-structured-data - Measure and Improve Code Quality continuously with Scrutinizer

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Push — master ( 83a312...2d3bb0 )

by Max

created 2018-07-20 01:20 UTC

structured_data.match.ProcessorList.init() A

↳ Parent: structured_data.match

Complexity

Conditions

Size

Total Lines	2
Code Lines	2

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	1
eloc	2
nop	2
dl	0
loc	2
rs	10
c	0
b	0
f	0

import collections
import keyword

from ._attribute_constructor import AttributeConstructor
from ._enum_constructor import EnumConstructor
from ._unpack import unpack


class MatchFailure(BaseException):
    """An exception that signals a failure in ADT matching."""


def desugar(constructor: type, instance: tuple) -> tuple:
    """Return the inside of an ADT instance, given its constructor."""
    if instance.__class__ is not constructor:
        raise MatchFailure
    return unpack(instance)


DISCARD = object()


class Pattern(tuple):
    """A matcher that binds a value to a name."""

    __slots__ = ()

    def __new__(cls, name: str):
        if name == '_':
            return DISCARD
        if not name.isidentifier():
            raise ValueError
        if keyword.iskeyword(name):
            raise ValueError
        return super().__new__(cls, (name,))

    @property
    def name(self):
        """Return the name of the matcher."""
        return self[0]

    def __matmul__(self, other):
        return AsPattern(self, other)


class AsPattern(tuple):
    """A matcher that contains further bindings."""

    __slots__ = ()

    def __new__(cls, matcher: Pattern, match):
        if match is DISCARD:
            return matcher
        return super().__new__(cls, (matcher, match))

    @property
    def matcher(self):
        """Return the left-hand-side of the as-match."""
        return self[0]

    @property
    def match(self):
        """Return the right-hand-side of the as-match."""
        return self[1]


def as_pattern_processor(target):
    def processor(value):
        if target is value:
            yield target.match
            yield target.matcher
        else:
            yield value
            yield value
    return processor


def enum_processor(target):
    def processor(value):
        yield from reversed(desugar(type(target), value))
    return processor


def tuple_processor(target):
    def processor(value):
        if isinstance(value, target.__class__) and len(target) == len(value):
            yield from reversed(value)
        else:
            raise MatchFailure
    return processor


class ProcessorList:

    def __init__(self, processors=()):
        self.processors = list(processors)

    def get_processor(self, item):
        for typ, meta_processor in self.processors:
            if isinstance(item, typ):
                return meta_processor(item)
        return None


PROCESSORS = ProcessorList((
    (AsPattern, as_pattern_processor),
    (EnumConstructor, enum_processor),
    (tuple, tuple_processor),
))


def not_in(container, name):
    if name in container:
        raise ValueError


def names(target):
    """Return every name bound by a target."""
    name_list = []
    names_seen = set()
    to_process = [target]
    while to_process:
        item = to_process.pop()
        if isinstance(item, Pattern):
            not_in(names_seen, item.name)
            names_seen.add(item.name)
            name_list.append(item.name)
        else:
            processor = PROCESSORS.get_processor(item)
            if processor:
                to_process.extend(processor(item))
    return name_list


def _as_name(key):
    if isinstance(key, Pattern):
        return key.name
    return key


class MatchDict(collections.abc.MutableMapping):

    def __init__(self):
        self.data = {}

    def __getitem__(self, key):
        key = _as_name(key)
        if isinstance(key, str):
            return self.data[key]
        if isinstance(key, tuple):
            return tuple(self[sub_key] for sub_key in key)
        if isinstance(key, dict):
            return {name: self[value] for (name, value) in key.items()}
        raise KeyError(key)

    def __setitem__(self, key, value):
        key = _as_name(key)
        if not isinstance(key, str):
            raise TypeError
        self.data[key] = value

    def __delitem__(self, key):
        del self.data[_as_name(key)]

    def __iter__(self):
        yield from self.data

    def __len__(self):
        return len(self.data)


def _match(target, value):
    match_dict = MatchDict()
    to_process = [(target, value)]
    while to_process:
        target, value = to_process.pop()
        if target is DISCARD:
            continue
        if isinstance(target, Pattern):
            not_in(match_dict, target.name)
            match_dict[target.name] = value
            continue
        processor = PROCESSORS.get_processor(target)
        if processor:
            to_process.extend(zip(processor(target), processor(value)))
        elif target != value:
            raise MatchFailure
    return match_dict


class ValueMatcher:
    """Given a value, attempt to match against a target."""

    def __init__(self, value):
        self.value = value
        self.matches = None

    def match(self, target):
        """Match against target, generating a set of bindings."""
        try:
            self.matches = _match(target, self.value)
        except MatchFailure:
            self.matches = None
        return self.matches is not None


pat = AttributeConstructor(Pattern)


__all__ = ['Pattern', 'ValueMatcher', 'desugar', 'names', 'pat']


1			import collections
2			import keyword
3
4			from ._attribute_constructor import AttributeConstructor
5			from ._enum_constructor import EnumConstructor
6			from ._unpack import unpack
7
8
9			class MatchFailure(BaseException):
10			"""An exception that signals a failure in ADT matching."""
11
12
13			def desugar(constructor: type, instance: tuple) -> tuple:
14			"""Return the inside of an ADT instance, given its constructor."""
15			if instance.__class__ is not constructor:
16			raise MatchFailure
17			return unpack(instance)
18
19
20			DISCARD = object()
21
22
23			class Pattern(tuple):
24			"""A matcher that binds a value to a name."""
25
26			__slots__ = ()
27
28			def __new__(cls, name: str):
29			if name == '_':
30			return DISCARD
31			if not name.isidentifier():
32			raise ValueError
33			if keyword.iskeyword(name):
34			raise ValueError
35			return super().__new__(cls, (name,))
36
37			@property
38			def name(self):
39			"""Return the name of the matcher."""
40			return self[0]
41
42			def __matmul__(self, other):
43			return AsPattern(self, other)
44
45
46			class AsPattern(tuple):
47			"""A matcher that contains further bindings."""
48
49			__slots__ = ()
50
51			def __new__(cls, matcher: Pattern, match):
52			if match is DISCARD:
53			return matcher
54			return super().__new__(cls, (matcher, match))
55
56			@property
57			def matcher(self):
58			"""Return the left-hand-side of the as-match."""
59			return self[0]
60
61			@property
62			def match(self):
63			"""Return the right-hand-side of the as-match."""
64			return self[1]
65
66
67			def as_pattern_processor(target):
68			def processor(value):
69			if target is value:
70			yield target.match
71			yield target.matcher
72			else:
73			yield value
74			yield value
75			return processor
76
77
78			def enum_processor(target):
79			def processor(value):
80			yield from reversed(desugar(type(target), value))
81			return processor
82
83
84			def tuple_processor(target):
85			def processor(value):
86			if isinstance(value, target.__class__) and len(target) == len(value):
87			yield from reversed(value)
88			else:
89			raise MatchFailure
90			return processor
91
92
93			class ProcessorList:
94
95			def __init__(self, processors=()):
96			self.processors = list(processors)
97
98			def get_processor(self, item):
99			for typ, meta_processor in self.processors:
100			if isinstance(item, typ):
101			return meta_processor(item)
102			return None
103
104
105			PROCESSORS = ProcessorList((
106			(AsPattern, as_pattern_processor),
107			(EnumConstructor, enum_processor),
108			(tuple, tuple_processor),
109			))
110
111
112			def not_in(container, name):
113			if name in container:
114			raise ValueError
115
116
117			def names(target):
118			"""Return every name bound by a target."""
119			name_list = []
120			names_seen = set()
121			to_process = [target]
122			while to_process:
123			item = to_process.pop()
124			if isinstance(item, Pattern):
125			not_in(names_seen, item.name)
126			names_seen.add(item.name)
127			name_list.append(item.name)
128			else:
129			processor = PROCESSORS.get_processor(item)
130			if processor:
131			to_process.extend(processor(item))
132			return name_list
133
134
135			def _as_name(key):
136			if isinstance(key, Pattern):
137			return key.name
138			return key
139
140
141			class MatchDict(collections.abc.MutableMapping):
142
143			def __init__(self):
144			self.data = {}
145
146			def __getitem__(self, key):
147			key = _as_name(key)
148			if isinstance(key, str):
149			return self.data[key]
150			if isinstance(key, tuple):
151			return tuple(self[sub_key] for sub_key in key)
152			if isinstance(key, dict):
153			return {name: self[value] for (name, value) in key.items()}
154			raise KeyError(key)
155
156			def __setitem__(self, key, value):
157			key = _as_name(key)
158			if not isinstance(key, str):
159			raise TypeError
160			self.data[key] = value
161
162			def __delitem__(self, key):
163			del self.data[_as_name(key)]
164
165			def __iter__(self):
166			yield from self.data
167
168			def __len__(self):
169			return len(self.data)
170
171
172			def _match(target, value):
173			match_dict = MatchDict()
174			to_process = [(target, value)]
175			while to_process:
176			target, value = to_process.pop()
177			if target is DISCARD:
178			continue
179			if isinstance(target, Pattern):
180			not_in(match_dict, target.name)
181			match_dict[target.name] = value
182			continue
183			processor = PROCESSORS.get_processor(target)
184			if processor:
185			to_process.extend(zip(processor(target), processor(value)))
186			elif target != value:
187			raise MatchFailure
188			return match_dict
189
190
191			class ValueMatcher:
192			"""Given a value, attempt to match against a target."""
193
194			def __init__(self, value):
195			self.value = value
196			self.matches = None
197
198			def match(self, target):
199			"""Match against target, generating a set of bindings."""
200			try:
201			self.matches = _match(target, self.value)
202			except MatchFailure:
203			self.matches = None
204			return self.matches is not None
205
206
207			pat = AttributeConstructor(Pattern)
208
209
210			__all__ = ['Pattern', 'ValueMatcher', 'desugar', 'names', 'pat']
211

mwchase / python-structured-data

Push — master ( 83a312...2d3bb0 )

structured_data.match.ProcessorList.__init__() A

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